Switching Points Research Articles

Метод снижения потерь энергии в импульсном преобразователе напряжения

A signal timing calculation method to control power switches of bidirectional switching converter (SC) with high efficiency is proposed. The method is applicable for MOSFET-based cascaded boost-buck converter, which has a negative offset current flow at the beginning of each conversion period. This current allows to perform turning on switches under zerovoltage and zero current switching condition to minimize switching losses. Meanwhile, the delay time between halfbridge transistors’ switching points is needed, when transistors’ output capacitances recharging takes place with following anti parallel body diode of transistor is being turned on unlocking. A proposed method is based on a switching delay time of input stage transistors valuation for the worst case of SC’s components’ parameters scatter, and provides guaranteed turning on of the upper transistor of the input stage under zero voltage and zero current condition. A clarified offset current calculation method is provided which introduces described time delays and SC’s input voltage.

The risk reducing of miners evacuation in case of an accident with aerological impact

Displacement of miners along emergency escape routes involves various types of risk. First of all, displacement of miners occurs rapidly in order to have time gap to carry out the evacuation within the operational time according to the emergency recovery plan. Further, the evacuation is carried out along routes that arranged far worse compared to that ones for the displacement of miners to their workplaces as well as escape routes provided with emergency ways. Further, strict compliance with regulations of the Safety Regulations for displacement along the gassy area of the route until reaching the nearest fresh stream and, after that, displacement exclusively along the clean stream, in some cases significantly increases the route length. For example, in case, when switching points as duplicate self-rescuers could be used, the exit during the operational time of the emergency recovery plan could be unreachable, while organizing of the second switching point is prohibited by the Safety Regulations, etc. In addition, the risk of emergency evacuation is due to the fact that, unlike classical route tasks, routes are built not “from point to point”, but from the initial set (the position of the emergency recovery plan) to the final one (the set of exits to the surface of mine shafts involved for evacuation). The individual risk differs for certain groups of miners evacuated from the workings according to the position of emergency recovery plan. Therefore, the study is devoted to the elaboration of a method reducing the risk of emergency evacuation with a probable (within acceptable limits) violation of the requirements of the Safety Regulations as well as correcting these regulations. Strict compliance with regulations of the Safety Regulations is able to complicate the emergency evacuation process. In modern mines provided with long and complicated ventilation networks, due to an exogenous fire outbreak, large gassy areas could be formed, which are, able to cause complications during emergency evacuation. Bypassing these areas means increasing the evacuation time that could lead to the exceeding of operational time according to the emergency recovery plan An algorithm for correction of escape routes is proposed, which, provided that real information about possible escape routes is obtained by means of an emergency simulation, will make it possible to shorten these routes, although they contain clean and gassy areas alternately. The algorithm is recommended for the discussion purpose in order to correct some regulations of the Safety Regulations. Keywords: emergency recovery plan, mine ventilation network, gassy area, emergency escape routes.

Procedure for regularization of bilinear optimal control problems based on a finite-dimensional model

An optimization problem of a linear system of ordinary differential equations on a set of piecewise continuous scalar controls with two-sided restrictions is considered. The cost functional contains the bilinear part (control, state) and a control square with a parameter, which plays the role of a regularization term. An approximate solution of the optimal control problem is carried out on a subset of piecewise constant controls with a non-uniform grid of possible switching points. As a result of the proposed parametrization, reduction to the finite-dimensional problem of quadratic programming was carried out with the parameter in the objective function and the simplest restrictions. In the case of a strictly convex objective function, the finite-dimensional problem can be solved in a finite number of iterations by the method of special points. For strictly concave objective functions, the corresponding problem is solved by simple or specialized brute force methods. In an arbitrary case, parameter conditions and switching points are found at which the objective function becomes convex or concave. At the same time, the corresponding problems of mathematical programming allow a global solution in a finite number of iterations. Thus, the proposed approach allows to approximate the original non-convex variation problem with a finite-dimensional model that allows to find a global solution in a finite number of iterations.

Estimation and Inference for High Dimensional Factor Model with Regime Switching

This paper proposes maximum (quasi)likelihood estimation for high dimensional factor models with regime switching in the loadings. The model parameters are estimated jointly by EM algorithm, which in the current context only requires iteratively calculating regime probabilities and principal components of the weighted sample covariance matrix. When regime dynamics are taken into account, smoothed regime probabilities are calculated using a recursive algorithm. Consistency, convergence rates and limit distributions of the estimated loadings and the estimated factors are established under weak cross-sectional and temporal dependence as well as heteroscedasticity. It is worth noting that due to high dimension, regime switching can be identified consistently right after the switching point with only one observation. Simulation results show good performance of the proposed method. An application to the FRED-MD dataset demonstrates the potential of the proposed method for quick detection of business cycle turning points.

Analysis on determining the solution of fourth-order fuzzy initial value problem with Laplace operator.

This study presents a new analytical method to extract the fuzzy solution of the fuzzy initial value problem (FIVP) of fourth-order fuzzy ordinary differential equations (FODEs) using the Laplace operator under the strongly generalized Hukuhara differentiability (SGH-differentiability). To this end, firstly the fourth-order derivative of the fuzzy valued function (FVF) according to the type of the SGH-differentiability is introduced, and then the relationships between the fourth-order derivative of the FVF and its Laplace transform are established. Furthermore, considering the types of differentiabilities and switching points, some fundamental theorems related to the Laplace transform of the fourth-order derivative of the FVF are stated and proved in detail and a method to solve FIVP by the fuzzy Laplace transform is presented in detail. An application of our proposed method in Resistance-Inductance circuit (RL circuit) is presented. Finally, FIVP's solution is graphically analyzed to visualize and support theoretical results.

Microscopic Disruption Management: Energy Consumption and Passenger Compensation Optimisation

Rail operations are often disrupted by accidents that cause traffic to diverge from the scheduled operations, rendering it difficult to run the schedule as planned. In such a case, the operator must change the schedule to return to the original schedule. If passengers are delayed, a train operator may have a policy of economically compensating them (e.g., refunding ticket fare). Compensation amounts are usually determined by the length of the delay. As a result, it is critical to have a smart way of determining whether to accelerate trains to absorb delays, thus increasing energy usage, or to compensate passengers. This paper presents a mathematical model for determining the speed profile while taking passenger usage into account. The model determines the best sequence of operating regimes and switching points between them for a variety of different situations and train types, all while accounting for delays and passenger compensation policies. The aim is to reduce both the amount of energy consumed and the amount of compensation paid to passengers. There are constraints on traction and braking forces, train velocity, forces induced by vertical and horizontal track profile, and passenger compensation policy. The results of computational tests performed on practical problem instances of the Spanish rail operator RENFE are showed. The suggested approach is capable of producing strategies that strike an excellent balance between different managerial objectives.

Improving of Railway Line Capacity Using Extended Station Switch Point Area

Improving of Railway Line Capacity Using Extended Station Switch Point Area

Necessary optimality conditions for two-step descriptor systems

<abstract><p>This paper is concerned with an optimal control problem for general two-step descriptor systems. Based on the nonsmooth analysis and variational techniques, we establish the first-order necessary optimality conditions. Then, due to the expression of the general solution for linear descriptor systems, which is established by virtue of the Drazin inverse, we derived the generalized second-order necessary conditions for the first time. Also, for unfixed switching point case, we give some discussions.</p></abstract>

Curved Turnouts for Curves of Various Radii

A methodology for calculation is proposed on the basis of the analysis of actual operating state and conditions of turnout points in order to develop a model range of curved turnouts that would meet the practical part of the radii. The key idea behind the development of such turnouts is to design specific switching points for curved parts of railway tracks that could reduce maintenance expenditures on curved turnouts and increase, if necessary, the travel speed through turnouts up to the ones when rounding a curve. The analysis of the data showed that the smallest shifts take place at small radii of easement curves. A general analysis of all calculation data is also made suggesting that it is advisable to lay concrete-beamed curved turnouts in curves of radii, which are larger or equal to those of the main track. In order to narrow the model range of concrete-beamed curved turnouts, there is examined a feasibility of precise alignment of turnouts and easements in curves, which corresponds well with the model range of curved turnouts on wooden beams. There is given a radius gradation as well as recommendations on laying-in of curved turnouts in order to meet any curve radius, where a turnout can be installed.

Оптимальное управление манипулятором

When solving the problem of optimal performance for manipulative robots, the scientific team headed by F. L. Chernousko actively uses the Pontryagin maximum principle. The application of the maximum principle is complicated by the nonlinearities of controlled systems of manipulation robots. Therefore, when using it, the original mathematical model is replaced with a simpler one. These substitutions made it possible to analytically solve the problems of finding the switching points of relay controls for individual models of manipulation robots. In this paper, when finding the switching moments of relay controls for a manipulating robot, the original nonlinear controlled system is used. The problem is reduced to the problem of the existence of a solution to the boundary value problem for a controlled nonlinear system in the selected class of permissible controls that guarantee the arrival of the manipulator in the final position with zero speeds.

Determination of colony characteristics and suitability for mass production of native Bombus terrestris L. population in the Central Black Sea coast region

In this study, two successive generations of queens belonging to a native Bombus terrestris population in the Central Black Sea Region of Türkiye were reared under controlled laboratory conditions to examine its developmental characteristics and suitability for mass production. The first generation was formed by a hundred Bombus terrestris queens which were caught from native fauna in Ordu Province, Türkiye. Young queens and males produced at the end of the life cycle in different colonies of first generation were mated in laboratory conditions. Mated queens were placed in a refrigerated incubator for their two months diapause period. After the diapause period, all queens were raised under the same conditions, and second generation colonies were reared. Some characters such as first egg-laying time, the timing of switch point, the timing of competition point, and total numbers of individuals produced in colonies of the first and second generation were determined. In these characteristics, the total numbers of workers and queens were found to be statistically significant between generations (p < 0.05). According to the findings of this study, some of the features such as first egglaying time, the timing of switch point, and the number of young queens produced may be unsatisfactory for mass production.

The Threshold Effect of Domestic Public Borrowing on the Nigerian Economy

TLike many other developing countries, the Nigerian government has increased domestic borrowing recently. This study examines the nonlinear relationship between domestic borrowing and economic growth, covering 1980 and 2019. The study adopts the threshold regression approach to establish the switching point between domestic borrowing and economic growth in Nigeria. The results reveal that the domestic borrowing and economic growth threshold is 14.88% of GDP with an inverted U-shaped curve. The maximum turning point of the variables implies the application of the debt Laffer Curve in Nigeria, showing that domestic borrowing is favourable to the economy before the threshold. However, additional domestic borrowing after the threshold induces an adverse effect on the economy. Also, the regression results of the non-varying threshold measures show that while the effect of external debt has been positive and significant on economic growth, gross fixed capital formation and inflation were negative and significant. Therefore, while recommending more rigorous monitoring and efficient utilisation of domestic borrowed funds by the government, the study emphasises the application of the threshold of 14.88% of GDP on domestic borrowing in the country.

Interacting with others while reacting to the environment.

Here, we revise Pietraszewski's model of groups by assigning participant pairs with two triplets, denoting: (1) the type of game that models the interaction, (2) its critical switching point between alternatives (i.e., the game's similarity threshold), and (3) the perception of strategic similarity with the opponent. These triplets provide a set of primitives that accounts for individuals' strategic motivations and observed behaviors.

Two Novel Dimorphism-Related Virulence Factors of Zymoseptoria tritici Identified Using Agrobacterium-Mediated Insertional Mutagenesis.

Diseases caused by dimorphic phytopathogenic and systemic dimorphic fungi have markedly increased in prevalence in the last decades, and understanding the morphogenic transition to the virulent state might yield novel means of controlling dimorphic fungi. The dimorphic fungus Z. tritici causes significant economic impact on wheat production, and yet the regulation of the dimorphic switch, a key first step in successful plant colonization, is still largely unexplored in this fungus. The fungus is amenable to suppression by fungicides at this switch point, and the identification of the factors controlling the dimorphic switch provides a potential source of novel targets to control Septoria tritici blotch (STB). Inhibition of the dimorphic switch can potentially prevent penetration and avoid any damage to the host plant. The aim of the current work was to unveil genetic determinants of the dimorphic transition in Z. tritici by using a forward genetics strategy. Using this approach, we unveiled two novel factors involved in the switch to the pathogenic state and used reverse genetics and complementation to confirm the role of the novel virulence factors and further gained insight into the role of these genes, using transcriptome analysis via RNA-Seq. The transcriptomes generated potentially contain key determinants of the dimorphic transition.

Physical parameters of neutrality in the work of an osteopathic physician

An osteopathic practitioner often meets the problem of physical fatigue, which is caused by a forced posture, excessive tension of the muscles of the trunk and arms, irrational biomechanical patterns of posture and movements, lack of support points, or switching points of mechanical energy of movement (fulcrum). These factors lead together to fatigue, which is felt as weariness and prevents the development of a pathophysiological state of overwork. Prevention of overwork by an osteopathic doctor can consist of a number of measures of labor organization and ergonomics, one of which is building a state of physical neutrality — a spatial position of the body that allows working with the patient as efficiently as possible and minimizing fatigue.

Risk Communication under Conflicting Information: The Role of Confidence in Subjective Risk Assessment

In this study, we develop a model of food consumption with a focus on the subjectively assessed risk of consumers and their degree of confidence in their risk assessment and use it to examine consumer behavior in the chaotic situation created by the Fukushima nuclear accident in 2011. The data were collected in March 2012 using a mail survey for 1300 Japanese women, the primary food purchasers. The respondents were asked to evaluate the cancer risk of eating agricultural products, which were assumed to be grown in the affected area, despite meeting national regulatory standards for radioactive materials, as a measure of their risk assessment and willingness to purchase Fukushima beef. The results show that the effect of confidence in a consumer&amp;rsquo;s risk assessment on their behavior depends on the stated risk level: when stated risk is below an estimated critical value, termed the switching point, the risk perceived by a consumer without confidence exceeds that of one with confidence. On the other hand, perceived risk is inversely related to confidence when the stated risk exceeds the switching point.

A transport model describing how defect accumulation leads to intrinsic dielectric breakdown and post-breakdown conduction

A charge transport model, originally developed for simulating time-dependent dielectric breakdown (TDDB) behavior at the interconnect level, was modified and extended to also apply to the current-voltage (I-V) behavior in the post-breakdown region. The model allows one to simulate the current-voltage characteristics of the dielectric material from its pristine state, through the wear-out and breakdown phase, and into the post-breakdown region. The systematic transition from the insulator region to the conductor-like region is visualized through the intrinsically generated trap distribution evolution. A percolation starts forming near the anode at a critical trap concentration of 5 × 1026m−3 for the system under study and proceeds directionally, towards the cathode. Soft breakdown occurs when the percolation path front reaches the cathode with a trap volume fraction of 0.15, close to the theoretical value of 0.16. Hard breakdown, at the switching point, is associated with the completion of a vacancy-type percolation path and saturation of the trap concentration. A power law relationship with a power of 2 is found between the system's conductance and the trap concentration near the anode between the critical point and the switching point. A predicted linear post-breakdown region following the breakdown event along with a weak temperature dependence agrees well with experimental observations.

Inflection Points, Kinks, and Jumps: A Statistical Approach to Detecting Nonlinearities

Inflection points, kinks, and jumps identify places where the relationship between dependent and independent variables switches in some important way. Although these switch points are often mentioned in management research, their presence in the data is either ignored, or postulated ad hoc by testing arbitrarily specified functional forms (e.g., U or inverted U-shaped relationships). This is problematic if we want accurate tests for our theories. To address this issue, we provide an integrative framework for the identification of nonlinearities. Our approach constitutes a precursor step that researchers will want to conduct before deciding which estimation model may be most appropriate. We also provide instructions on how our approach can be implemented, and a replicable illustration of the procedure. Our illustrative example shows how the identification of endogenous switch points may lead to significantly different conclusions compared to those obtained when switch points are ignored or their existence is conjectured arbitrarily. This supports our claim that capturing empirically the presence of nonlinearity is important and should be included in our empirical investigations.

Are colorectal surgery patients willing to accept an increased risk of surgical site infection to avoid mechanical bowel preparation? Implications for future trial design.

Recent evidence has shown no difference in the risk of surgical site infection (SSI) with oral antibiotics alone (OA) and oral antibiotics in combination with mechanical bowel preparation (OA+MBP), suggesting that the use of MBP may be safely avoided. The aim of this work was to determine the absolute risk of SSI that patients would accept with OA relative to OA+MBP. Standardized, in-person interviews were conducted using the threshold task with patients attending colorectal surgery clinics who had previously had MBP. Participants were asked which option they preferred when the absolute risk of SSI was 7% for both options. Next, their switch point was determined by increasing the risk of SSI with OA by 1% intervals until their preference changed from OA to OA+MBP. Median switch point scores were reported and represented the absolute increased risk of SSI that patients would accept with OA relative to OA+MBP. Fifty patients completed the interview. All participants chose OA over OA+MBP when the risk of SSI was 7% for both options. Switch points ranged from 8% to 25%, with a median of 10%, indicating that participants were willing to accept up to a 3% increase in absolute risk of developing a SSI with OA to avoid MBP. The results showed that patients are willing to accept an increased risk of up to 3% for SSI with OA relative to OA+MBP. Incorporating patient preferences into the planning of future trials has the potential to improve the uptake of trial results into clinical practice.

Effects of Dietary Protein Concentration on Lipid Metabolism Gene Expression and Fatty Acid Composition in 18-23-Month-Old Hanwoo Steers.

Simple SummaryIntramuscular fat or fatty acids content was regarded as a quality index of meat as it increases meat tenderness and flavor. In Korea, commercial Hanwoo farms have been supplying concentrate feeds that are 2–3% higher in crude protein (CP) content rather than conventional feeds throughout the entire program and have tried to shorten the feeding period to less than 28 months of age. This has led to a probable stability in lean-to-fat ratio in Hanwoo steers from 19 to 21 months of age. This stability could be linked to the regulation of the gene expression mediating lipogenesis during this phase. However, there is a lack of data regarding the effects of the protein level in isoenergetic concentrate diets on transcriptional activity of such genes at this phase. The conventional feeding program and the current one with relatively higher CP content were compared in two groups of twenty Hanwoo steers. Results showed that higher CP endorsement during the growing phase increased the expression of intramuscular PPARα (p < 0.1) and LPL (p < 0.05) and decreased the genes, such as VLCAD (p < 0.01), GPAT1 (p = 0.001), and DGAT2 (p = 0.016), which are involved in lipogenesis and fatty acid esterification. This may result in a relatively lower lipid turnover which could be responsible for shortening the feeding period.The present study evaluated the influence of dietary protein level on growth performance, fatty acid composition, and the expression of lipid metabolic genes in intramuscular adipose tissues from 18- to 23-month-old Hanwoo steers, representing the switching point of the lean-to-fat ratio. Forty steers with an initial live weight of 486 ± 37 kg were assigned to one of two treatment groups fed either a concentrate diet with 14.5% CP and or with 17% CP for 6 months. Biopsy samples of intramuscular tissue were collected to analyze the fatty acid composition and gene expression at 23 months of age. Throughout the entire experimental period, all steers were restrained twice daily to allow individual feeding. Growth performance, blood metabolites, and carcass traits, according to ultrasonic measurements, were not affected by the experimental diets. The high-protein diet significantly increased the expression of intramuscular PPARα (p < 0.1) and LPL (p < 0.05) but did not affect genes involved in fatty acid uptake (CD36 and FABP4) nor lipogenesis (ACACA, FASN, and SCD). In addition, it downregulated intramuscular VLCAD (p < 0.01) related to lipogenesis but also GPAT1 (p = 0.001), DGAT2 (p = 0.016), and SNAP23 (p = 0.057), which are involved in fatty acid esterification and adipocyte size. Hanwoo steers fed a high-protein diet at 18–23 months of age resulted in a relatively lower lipid turnover rate than steers fed a low-protein diet, which could be responsible for shortening the feeding period.