OBSERVER’S TRAJECTORY TRACKING OBJECT BYPASSING OBSTACLE ON THE SHORTEST CURVE

Motion of some object is considered. The object t moves from the initial point t∗ to the final one t ∗ . But since absent of the direct path, he should bypass an obstacle a connected bodily set G. It is supposed that t moves by the most short trajectory T = Tt , and the trajectory T is a convex curve. The observer’s f task is to find the trajectory Tf that provides tracking the object on the most part of the object’s motion and, if possible, the lesser object’s stealth of motion along the trajectory T . The latency is defined by the distance that the observer must pass to see the object in the field of vision. The object and observer start at the same initial instant, and their velocities are equal. In the paper, examples of the trajectories Tf in R 2 are presented, on which the observer can see the object’s trajectory T ; also, the value of the object’s latency is shown for the invisible parts of the trajectory T . The variant of Tf in R 3 is shown.

A Novel Analysis of the Smooth Curve with Constant Width Based on a Time Delay System

In this paper, we analyze the C∞ smooth curve of constant width using the characteristic equation of a time delay system. We prove that a closed convex curve must be a circle if it is still a smooth curve of constant width after taking any number of derivatives. Finally, the simulation results are presented for analyzing the influence of derivative orders on a smooth non-circular curve of constant width.

Dip angles of active faults from the surface to the seismogenic zone inferred from a 2D numerical analysis of visco-elasto-plastic models: a case study for the Osaka Plain

The geometries (i.e., dip angles) of active faults from the surface to the seismogenic zone are the most important factors used to evaluate earthquake ground motion, which is crucial for seismic hazard assessments in urban areas. In Osaka, a metropolitan city in Japan, there are several active faults (e.g., the Uemachi and Ikoma faults), which are inferred from the topography, the attitude of active faults in surface trenches, the seismic reflection profile at shallow depths (less than 2 km), and the three-dimensional distribution of the Quaternary sedimentary layers. The Uemachi and Ikoma faults are N–S-striking fault systems with total lengths of 42 km and 38 km, respectively, with the former being located ~ 12 km west of the latter; however, the geometries of each of the active faults within the seismogenic zone are not clear. In this study, to examine the geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone, we analyze the development of the geological structures of sedimentary layers based on numerical simulations of a two-dimensional visco-elasto-plastic body under a horizontal compressive stress field, including preexisting high-strained weak zones (i.e., faults) and surface sedimentation processes, and evaluate the relationship between the observed geological structures of the Quaternary sediments (i.e., the Osaka Group) in the Osaka Plain and the model results. As a result, we propose geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone. When the friction coefficient of the faults is ~ 0.5, the dip angles of the Uemachi and Ikoma faults near the surface are ~ 30°–40° and the Uemachi fault has a downward convex curve at the bottom of the seismogenic zone, but does not converge to the Ikoma fault. Based on the analysis in this study, the dip angle of the Uemachi fault zone is estimated to be approximately 30°–40°, which is lower than that estimated in the previous studies. If the active fault has a low angle, the width of the fault plane is long, and thus the estimated seismic moment will be large.

Determination of parameters of pipeline repair with initial curvature

Ремонт трубопровода часто предусматривает его подъем трубоукладчиками, что предполагает перемещение заполненной трубы в вертикальной и горизонтальной плоскостях. Для обеспечения безопасности проведения ремонтных работ необходима оценка напряженно-деформированного состояния ремонтируемого участка. Известна методика определения технологических параметров ремонта при перемещении прямолинейного трубопровода. Однако почти всегда трубопровод имеет начальную кривизну оси. В этой связи разработана методика определения технологических параметров ремонта участков подземного трубопровода с начальной кривизной оси. Проведен сравнительный анализ параметров ремонта методом изменения положения трубопровода с начальной кривизной и прямолинейного трубопровода. Приведены основные положения методики расчета. Рассмотрены случаи изгиба трубопровода в вертикальной плоскости выпуклостью вниз (вогнутая кривая) и выпуклостью вверх (выпуклая кривая), а также деформирование при разрезке. Исследована зависимость параметров ремонта от знака начальной кривизны участка трубопровода. Методика может быть использована при планировании ремонтных работ для определения нагрузок на крюки трубоукладчиков, расстояния между трубоукладчиками, высоты подъема (дозаглубления) трубопровода, протяженности ремонтируемого участка (участка вскрытия траншеи), а также для расчета вертикального перемещения и угла поворота торца реза при установлении геометрических параметров кривой вставки. Pipeline repairs often involve lifting by pipe-layers, which involves moving the filled pipe in both vertical and horizontal planes. To ensure the safety of repair work, it is necessary to assess the stress-strain state of the repaired area. There is a technique for determining the technological parameters of repair when moving a straight pipeline. However, the pipeline almost always has an initial axis curvature. Accordingly, an urgent scientific and practical task is to assess the influence of pipeline initial curvature on technological parameters of repair. For this purpose, a method has been developed for determining the technological parameters of repairing sections of an underground pipeline with initial axis curvature. A comparative analysis of the repair parameters by changing the position of pipeline with initial curvature and straight pipeline is carried out. Then the main provisions of the calculation method are given. Cases of pipeline bending in the vertical plane with a downward convexity (concave curve) and upward convexity (convex curve), as well as deformation during cutting, are considered. The dependence of repair parameters on initial curvature sign of the pipeline section is investigated. The technique can be used when planning repair work to determine pipe-layer hook loads, the distance between pipe-layers, the height of the pipeline rise (additional deepening), length of the section to be repaired (trench opening section), as well as for calculating the vertical displacement and angle of rotation of the cut end when establishing geometric parameters insertion curve.

Prevalence and stability of SARS CoV-2 RNA on Bangladeshi banknotes

Originating at December 2019 in China, SARS-CoV-2 has emerged as the deadliest pandemic in the history of mankind. Along with direct contact and droplet contaminations, possibility of infections through contaminated surfaces and fomites are being investigated. In this study, we aim to assess the prevalence of SARS-CoV-2 viral RNA by real time one-step reverse transcriptase PCR on banknotes being circulating in Bangladesh. We also assessed the persistence of the virus on banknotes spiked with SARS-CoV-2 positive diluted human nasopharyngeal samples. Among the 425 banknote samples collected from different entities, 7.29% (n= 31) were tested positive for targeted genes. Twenty four representative positive samples were assessed for N gene fragments by conventional PCR and sequenced. All the samples carry viral RNA belonged to GR clade, the predominant circulating clade in Bangladesh. In the test of stability, the N gene was detected for up to 72 h on banknotes spiked with nasopharyngeal samples and CT values increases significantly with time (p<0.05). ORF1b gene was observed to be less stable specially on old banknotes and usually went beyond detectable limit within 8 to 10 h. The stability of virus RNA was well fitted by Weibull model and concave curve for new banknotes and convex curve for old banknotes have been revealed. Handling of banknotes is unavoidable; hence these findings implicated that in order to limit SARS-CoV-2 transmission through banknotes proper hygiene practice are needed.

Female fiddler crabs, Austruca lactea (Decapoda: Ocypodidae), adjust their rate of mate sampling based on remaining days until oviposition under a size-dependent temperature constraint

Rate of mate sampling is one of the critical components associated with sampling costs in female mate choice. In ectotherms, environmental temperature generally constrains locomotion performance. In addition, females will adjust the mate sampling rate depending on their breeding schedule because of the risk of remaining unfertilized eggs or a loss of benefits related to mating, if they lose the opportunity to copulate. This study investigated how these effects influence the rate of female mate sampling in the temperate fiddler crab (Austruca lactea) in the field. The number of sampled males per searching duration formed a convex curve against environmental temperature. The optimal environmental temperature increased with the female body size. These results suggest that mate sampling rate is under a size-dependent temperature constraint, and sampling costs are lower for larger females than smaller individuals under high-temperature conditions. Furthermore, when there were fewer remaining days, the mate sampling rate increased. Females would hasten the sampling rate to ensure a suitable burrow for breeding. Mate sampling rate in female A. lactea is therefore associated with environmental temperature, female body size and remaining days until oviposition.

Evaluation of Dip Angles of Active Faults Beneath the Osaka Plain Inferred from a 2D Numerical Analysis of visco-elasto-plastic Models

The geometries (i.e., dip angles) of active faults from the surface to the seismogenic zone are among the most important factors used to evaluate earthquake ground motion, which is crucial to seismic hazard assessments in urban areas. In Osaka, a metropolitan city in Japan, there are several active faults (e.g., the Uemachi and Ikoma faults), which are inferred from the topography, the attitude of active faults in surface trenches, the seismic reflection profile at shallow depths (less than 2 km), and the three-dimensional distribution of the Quaternary sedimentary layers. The Uemachi and Ikoma faults are N–S-striking fault systems with total lengths of 42 km and 38 km, respectively, with the former being located ~12 km west of the latter; however, the geometries of each of the active faults within the seismogenic zone is not clear. In this study, to examine the geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone, we analyze the development of the geological structures of sedimentary layers based on numerical simulations of a two-dimensional visco-elasto-plastic body under a horizontal compressive stress field, including preexisting linear high-strained weak zones (i.e., faults) and surface sedimentation processes, and evaluate the relationship between the observed geological structures of the Quaternary sediments (i.e., the Osaka Group) in the Osaka Plain and the model results. Based on a comparison between the simulation results and the geological observations/interpretation, we propose geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone. When the friction coefficient of the faults is ~0.5, the dip angles of the Uemachi and Ikoma faults near the surface are ~30°–40° and the Uemachi fault has a downward convex curve at the bottom of the seismogenic zone but does not converge to the Ikoma fault. Based on the analysis in this study, the dip angle of the Uemachi fault zone is estimated to be approximately 30°–40°, and the downward extension of the Uemachi fault zone nearly coincides with the epicenter of the 2018 northern Osaka earthquake.

An Innovative Method for Conventional Triaxial Tests of Concrete: Applications of PVC Pipes as a Mould and Sealing Membrane

In this paper, we propose an innovative method for conventional triaxial tests of concrete with a confining cell. The polyvinyl chloride (PVC) pipe is used as a mould to cast concrete and also as a membrane to isolate the concrete specimen from oil under confinements. This method is termed as PMM (i.e., PVC pipe is used as a mould and membrane). However, a heat-shrink sleeve is used as a membrane in the traditional test method (TMM). Specimens were made from mortar without coarse aggregates in the present experiment. Under six confinements (0–70 MPa), the conventional triaxial compression tests were performed on ultrahigh-strength (150 MPa) and high-strength (82 MPa) mortar specimens by PMM and TMM. The results indicate the following: (i) there is a characteristic confinement p0; when the confinement is lower than p0, the strength by PMM is higher than that by TMM; on the contrary, when the confinement is higher than p0, the strengths by both methods are almost identical. In this work, p0 is between 0 and 5 MPa. (ii) When the confinement is 5–70 MPa, the relationship between the peak stress of high-strength mortar and confinement is characterized by a monotonically rising straight line; however, a monotonically rising upward convex curve describes the peak stress of ultrahigh-strength mortar related to the confinement. (iii) The residual strength using PMM is significantly higher than that using TMM at zero confinement or lower confinements, but the residual strengths by these two methods are approximately identical at higher confinements. (iv) The transverse cracks appear in the mortar specimen inside the PVC pipe after enduring a triaxial loading using PMM. However, there is no such phenomenon when TMM is applied.

Study on the Compressive Properties of Magnesium Phosphate Cement Mixing with Eco-Friendly Coir Fiber Considering Fiber Length

Coir fiber (CF), an eco-friendly and renewable natural fiber, was introduced into magnesium phosphate cement (MPC) mortar to improve its crack resistance. A total of 21 specimens were employed to investigate the failure pattern, compressive strength, stress–strain curve, and energy absorption of MPC with varying CF lengths (0, 5, 10, 15, 20, 25, and 30 mm) after a curing period of 28 days through a static compressive test. The results demonstrated that compressive strength, elastic modulus, and secant modulus decreased with the increase in CF length. However, energy absorption presented a convex curve, which increased to the maximum value (77.0% relative to the value of the specimen without CF) with a CF length of 20 mm and then declined. A series of modern micro-tests were then carried out to analyze the microstructure and composition of specimens to explain the properties microscopically.

The Paradox of “Eyes on the Street”: Pedestrian Density and Fear of Crime in Yaoundé, Cameroon

Most studies highlighting the link between the urban environment and fear of crime (FoC) have focused on less populated spaces in urban areas, and concluded that the presence of activities and people in a space makes its users more confident. This study analyses the paradoxical phenomenon of FoC in occupied public spaces in the setting of Yaoundé, Cameroon. To this end, this study analyses the relationship between intersection level, pedestrian density and perceived FoC. The results of the multi-level binary logistic regression demonstrate that women, vulnerable age groups, people with a weak sense of community and high-income people tend to express a higher level of FoC. Among the major FoC theories, these results confirm the theories of physical vulnerability and social networks and invalidate the theory of social vulnerability in the local context. The results also reveal that the relationship between “pedestrian density” and FoC seems to be a convex curve with the minimum value, implying that the concept of ‘eyes on the street’ is not valid in places where pedestrian density exceeds a specific threshold. This suggests that policy makers and planners should consider pedestrian density when designing public spaces, not only to secure wellbeing, but also due to the impact it can have on perceived FoC among those who use such spaces.