Conical picks of mining machines with increased utility properties – selected construction and technological aspects

Shearers and roadheaders are commonly used to extract useful mineral deposits, especially hard coal, and for drilling roadways in underground mines, tunnels and other underground buildings in civil engineering. As the primary working process of this type of machines, mechanical mining of rocks is carried out by cutting. These machines' working units are equipped for this purpose with picks, usually conical (point-attack). They have the form of an axially symmetrical body consisting of a steel shaft and a tip usually made of tungsten carbide, connected by a hard brass solder. Due to the possibility of spontaneous rotation in the pick holders and even wear and tear of their tip around the entire perimeter, conical picks have a much longer service life compared to radial picks. Their life, especially when cutting hard and sharp abrasive rocks, is, however, still unsatisfactory. Rapid wear of the picks leads to a decrease in mining efficiency, an increase in this process's energy consumption, and an increase in dynamic surplus to which the cutting machine is subject. Among many forms of wear and tear of the conical picks, attention was paid to the problem of asymmetrical abrasive wear of the tips, pulling out the connection of the soldered pick tip and fatigue breaking of the pick shafts in the transition zone of the shank into the shoulder. The article presents original propositions of modification of the construction of the roadheaders/shearers conical pick shafts and the method of fixing the tip in the pick shaft in order to increase their operational durability significantly. The technologies and devices necessary to manufacture conical picks of the proposed structure were described. The developed modifications significantly contribute to the improvement of functional properties, including the reliability of conical picks, used in particular for hard rock mining.

How Asymmetries Evolved: Hearts, Brains, and Molecules

Humans belong to the vast clade of species known as the bilateria, with a bilaterally symmetrical body plan. Over the course of evolution, exceptions to symmetry have arisen. Among chordates, the internal organs have been arranged asymmetrically in order to create more efficient functioning and packaging. The brain has also assumed asymmetries, although these generally trade off against the pressure toward symmetry, itself a reflection of the symmetry of limbs and sense organs. In humans, at least, brain asymmetries occur in independent networks, including those involved in language and manual manipulation biased to the left hemisphere, and emotion and face perception biased to the right. Similar asymmetries occur in other species, notably the great apes. A number of asymmetries are correlated with conditions such as dyslexia, autism, and schizophrenia, and have largely independent genetic associations. The origin of asymmetry itself, though, appears to be unitary, and in the case of the internal organs, at least, may depend ultimately on asymmetry at the molecular level.

Does Asymmetrical Gonopodium Morphology Predict Lateralized Behavior in the Fish Xenophallus umbratilis?

Why bilaterally symmetrical organisms express handedness remains an important question in evolutionary biology. In some species, anatomical asymmetries have evolved that accompany behavioral handedness, yet we know remarkably little about causal links between asymmetric morphological traits and behavior. Here, we explore if a dextral or sinistral orientation of the male intromittent organ predicts side preferences in male behaviors. Our study addresses this question in the Costa Rican livebearing fish, Xenophallus umbratilis. This fish has a bilaterally symmetrical body plan, with one exception—the male anal fin (gonopodium), used to inseminate females, terminates with a distinct left- or right-handed corkscrew morphology. We used a detour assay to test males for side biases in approach behavior when exposed to four different stimuli (predator, potential mate, novel object, empty tank control). We found that left morph males preferred using their right eye to view potential mates, predators, and the control, and that right morph males preferred to use their left eye to view potential mates and predators, and their right eye to view the control. Males of both morphs displayed no eye bias when approaching the novel object. Our results suggest that there is a strong link between behavior and gonopodium orientation, with right and left morph males responding with opposite directional behaviors when presented with the same stimuli. This presents the intriguing possibility that mating preferences—in this case constrained by gonopodial morphology—could be driving lateralized decision making in a variety of non-mating behaviors.

ENGLISH AND INDONESIAN GREETINGS AS ADJACENCY PAIRS: A PRAGMATIC STUDY

A speaker customarily opens the conversation by saying greeting to his or her interlocutor. At a glance, greetings maybe not a complicated activity but for the most part, they are highly conventionalized and follow patterned routines. Despite it, the pattern or sequence of greetings along with its type is dynamic and developed. The research aimed to describe the kinds of verbal and non-verbal greetings customarily shown in every exchange, to reveal the sequence of English and Indonesian greetings as adjacency pairs in social exchange. The data consists of English collected from "Twelve Years a Slave" while Indonesian data are obtained from observation, record, and field notes. Both of the data are analyzed by using descriptive qualitative method. The result of this research indicates that there are four types of Indonesian sequential greetings uncovered by Firth's theory, characterized by interjection-question, question-body language, interjection-invitation, and invitation. Each is used in a single utterance for each pair. Second, English data indicate the sequences of greetings uttered by first pair and second are symmetrical, body language preceding question, and body language, on the other hand, Indonesian greeting sequence, the researcher finds an asymmetrical pattern, question preceding question, body language, and visual response. Miscellaneous greeting sequences also appeared in both such as affirmation and facial expression, question and affirmation, affirmation and invitation, invitation and affirmation, and also question and direct answer.

A Systematic Review of the Impact of Sports on Body Posture in Adolescents

Purpose: A correct body posture plays an important role in people’s health, especially for children and adolescents who are in intensive development. Exercise regularly can increase their health, but there is also an adverse influence on children and adolescents. Thus this review evaluates the impacts of basketball, volleyball, football, gymnast training on the body posture of adolescents. Methods: The literature collect was complete through databases which included Google Scholar, PubMed, and ScienceDirect. Eight of 480 studies met the inclusion criteria. The collecting articles have assessed the impact of the sport of basketball, volleyball, football, and gymnast on body posture. Result and Conclusion: According to the analysis, the sport of basketball and volleyball play a negative effect on adolescent’s body posture and deviation of body posture increase as training time longer. Further research is required to be done to investigate football training to affect body posture because no studies are confirming the effect of football on body posture. However, gymnast training showed a symmetrical body posture, but the changes of the spine in the sagittal plane in adolescents are worthy of attention. Therefore, it is important to notice that the training program not only aims at the outcome but also promote the harmonious development of the adolescent.

Overcoming the detectability costs of symmetrical coloration

For camouflaged prey, enhanced conspicuousness due to bilaterally symmetrical coloration increases predation risk. The ubiquity of symmetrical body patterns in nature is therefore paradoxical, perhaps explicable through tight developmental constraints. Placing patterns that would be salient when symmetrical (e.g. high contrast markings) away from the axis of symmetry is one possible strategy to reduce the predation cost of symmetrical coloration. Artificial camouflaged prey with symmetrical patterns placed at different distances from the axis were used in both visual search tasks with humans and survival experiments with wild avian predators. Targets were less conspicuous when symmetrical patterning was placed outside a ‘critical zone’ near the midline. To assess whether real animals have evolved as predicted from these experiments, the saliency of features at different distances from the midline was measured in the cryptically coloured forewings of 36 lepidopteran species. Salience, both in absolute terms and relative to wing area, was greatest away from the axis of symmetry. Our work, therefore, demonstrates that prey morphologies may have evolved to exploit a loophole in the ability of mammalian and avian visual systems to spot symmetrical patterns.

A general model of locomotion of brittle stars with a variable number of arms

Typical brittle stars have five radially symmetrical arms that coordinate to move the body in a certain direction. However, some species have a variable number of arms, which is a unique trait since intact animals normally have a fixed number of limbs. How does a single species manage different numbers of appendages for adaptive locomotion? We herein describe locomotion in Ophiactis brachyaspis with four, five, six and seven arms to propose a common rule for the movement of brittle stars with different numbers of arms. For this, we mechanically stimulated one arm of individuals to analyse escape direction and arm movement. By gathering quantitative indices and employing Bayesian statistical modelling, we noted a pattern: regardless of the total number of arms, an anterior position emerges at one of the second neighbouring arms to a mechanically stimulated arm, while arms adjacent to the anterior one synchronously work as left and right rowers. We propose a model in which an afferent signal runs clockwise or anticlockwise along the nerve ring while linearly counting how many arms it passes through. With this model, the question on how ‘left and right’ emerges in a radially symmetrical body via a decentralized system is answered.

Generalized locomotion of brittle stars with a flexible number of arms

Typical brittle stars have five radially symmetrical arms, which coordinate to move their body in a certain direction. However, some species of them show individual difference in the number of arms. We found this trait unique since intact legged animals each own a fixed number of limbs in general. How does a single species manage such different numbers of motile organs to realize adaptive locomotion? We here described four-, five-, six-, and seven-armed locomotion with the aim to generalize a common rule which is flexible with arm numbers in brittle stars. We mechanically stimulated an arm inOphiactis brachyaspisto analyze escape direction and arm movements. Gathering quantitative indices and employing Bayesian statistical modeling, we figured out an average locomotion: regardless of the total number of arms, a front position emerges at one of the second neighboring arms to a mechanically stimulated arm, while side arms adjacent to the front synchronously work as left and right rowers. We suggest a model where some afferent signal runs either clockwise or anticlockwise along the nerve ring while linearly counting how many arms it passes. This idea would explain how ‘left and right’ emerges in a radially symmetrical body via a decentralized system.

Imperforate anus in symmetrical conjoined live twins

This is a case report of newly born twins. The live twins were with two separate heads and a symmetrical body, conjoined in a sagittal plane. Their thorax and abdomen were broader then singleton normal. Spines were separate in cervical regions but gradually approached each other and completely fused at sacrum. Single perineum had an imperforate anus.

Aerodynamics Analysis on Unsymmetrical Fuselage Models

The large commercial passengers airplanes are mostly designed to have symmetrical body with respect to the longitudinal axis. However for small passengers airplanes or for the airplane designed as UAV plat form is normally having an unsymmetrical fuselage. The aerodynamics characteristics fuselage may give a strong influence to the overall aerodynamics characteristics of the airplane. The present work investigates the aerodynamics characteristics of the unsymmetrical fuselage with respect to the longitudinal axis. The fuselage assumed to have circular cross section and the coordinate of the fuselage are created by using the same equation which had been used in defining the coordinate of cambered airfoil NACA series four digits. The fuselage had been set to have the same maximum thickness 15 % of the fuselage length and different fuselage models are obtained through varying the position as well as the value of the maximum camber line. The semi empirical aerodynamic method for estimating the fuselage lift coefficient CL, drag coefficient CDand the fuselage pitching moment coefficient CMsuch as given by DATCOM are well established. However when it came to the unsymmetrical fuselage, this approach can not be adopted easily. The required of angle attack at zero lift of the corresponding unsymmetrical fuselage is difficult to define. The result for particular cambered fuselage indicates that the aerodynamics characteristics strongly influenced by how the fuselages camber lines look likes.