Study on Blasting Technology for Open-Pit Layering of Complex Mine Adjacent to High and Steep Slope

In China, mining blasting vibration has seriously threatened the safety and stability of high and steep rock slopes. In this paper, taking the east mining area of Jianshan Phosphorus Mine as the research background, combined with field survey, field blasting test, numerical simulation and theoretical analysis, we systematically studied the adjacent high-steep rock slope and the layered blasting technology of complex ore. Based on wide hole spacing blasting numerical simulation and field tests, the use of 8 × 4 m hole network parameters, oblique line hole-by-hole initiation method, detonator delay using 35 ms between holes, 65 ms between rows and 500 ms within the holes, the rock mass rate was reduced and the drilling workload was decreased. In addition, regression analysis was carried out on a large amount of vibration test data, and the attenuation law and propagation law of blasting vibration of adjacent high and steep slopes were predicted, which provided a reference for mine production blasting. By establishing a mathematical model of cumulative damage of rock mass blasting, it shows that the depth of impact of mining blasting on the slope of Jianshan open-pit was 0–3.6m, but the blasting did not cause overall damage to the adjacent high and steep slopes. In the future, this model can be used to predict rock damage caused by subsequent blasting.

Experimental Study on the Shear Band of Methane Hydrate-Bearing Sediment

The occurrence of a shear band is often thought as the precursor of failure. To study the initiation of shear banding in gas hydrate-bearing sediments, two groups of triaxial compression tests combined with a CT (computer tomography) scan were conducted by triaxial CT-integrated equipment under two confining pressures and seven hydrate saturations. The macro stress–strain curves and the corresponding CT scanning images of the micro-structure and the distribution of the components were obtained. The geometric parameters of the shear bands were measured based on the CT images at four typical axial strains, respectively. The distribution characteristics of soil particles, water, hydrate and gas were also analyzed. It is shown that the existence of methane hydrate changes the mechanical property of hydrate-bearing sediment from plastic failure to brittle failure when the hydrate saturation is over 13%, which occurs in the range of the tests in this paper. The peak of the deviatoric stress increases with the hydrate saturation. The shear band is in either a single oblique line or inter-cross lines depending on the hydrate saturation, the effective confining pressure and the initial distribution of the gas hydrate. Most of the shear band surfaces are not straight, and the widths of the shear bands are almost non-uniformly distributed.

Viscera of the neck

The thyroid gland is a symmetrical H-shaped endocrine structure in the lower neck. It consists of two lobes, each extending from the oblique line of the thyroid cartilage above to the sixth tracheal ring below – united by a median isthmus covered by the anterior jugular veins. The small, (usually) paired and inconsistent parathyroid glands lie behind the lobes of the thyroid gland. They measure 6mm by 4mm by 2mm and are ordinarily four in number – two superior and two inferior. They are involved in the careful regulation of the body’s calcium levels. Both superior and inferior glands are ordinarily supplied by the inferior thyroid artery. Drainage is into the venous plexus on the anterior surface of the thyroid.

Design and Performance Evaluation of a Single-Phase Driven Ultrasonic Motor Using Bending-Bending Vibrations

An ultrasonic motor as a kind of smart material drive actuator has potential in robots, aerocraft, medical operations, etc. The size of the ultrasonic motor and complex circuit limits the further application of ultrasonic motors. In this paper, a single-phase driven ultrasonic motor using Bending-Bending vibrations is proposed, which has advantages in structure miniaturization and circuit simplification. Hybrid bending vibration modes were used, which were excited by only single-phase voltage. The working principle based on an oblique line trajectory is illustrated. The working bending vibration modes and resonance frequencies of the bending vibration modes were calculated by the finite element method to verify the feasibility of the proposed ultrasonic motor. Additionally, the output performance was evaluated by experiment. This paper provides a single-phase driven ultrasonic motor using Bending-Bending vibrations, which has advantages in structure miniaturization and circuit simplification.

Mandibular dentigerous cyst: Enucleation and bone reconstruction – Case report

Purpose: The dentigerous cyst is the second most common odontogenic cyst in the jaws. These lesions are observed in routine examinations. The third molars and maxillary canines are the most affected teeth. Definition of marsupialization and enucleation techniques as well as consideration of important objective criteria for the treatment plan like cyst size, age, and proximity to anatomical structures, clinical importance of the tooth or teeth associated with the lesion and risk of bone fracture. This paper will present a case report treated by maneuver of decompression followed by enucleation and bone reconstruction. Case report: A 43-year-old female patient, Caucasian, attended the Oral-Maxillofacial Surgery consultation at Clitrofa - Centro Médico, Dentário e Cirúrgico, in Trofa - Portugal, to assess extraction of 3.8 and 4.8. On intraoral physical examination, a slight bulging of the cortical bone was noted in the region of the left external oblique line. Aspiration puncture was performed and a small amount of light-yellow liquid confirmed the cystic nature of the lesion. In a second stage, osteotomy through piezoelectric surgery was performed. The cystic capsule was excised together with the extraction of tooth 3.8 included and tooth 3.7. Bone regeneration was performed. The material obtained from the cystic cavity was sent for pathological examination, confirming the diagnosis of dentigerous cyst. During observation of the patient for twelve months, no hypoesthesia or any sign of recurrence of the lesion was observed. Conclusion: The technique preserved the neurosensory function and was effective for the enucleation and reconstruction of the lesion. Despite the clinical peculiarities of each case and the chosen treatment method, the prognosis of these lesions is favourable when appropriate therapy is used.

ASSESSMENT OF ANATOMICAL CONDITIONS FOR THE INSTALLATION OF MINISCREWS «BIORAY A1» IN THE AREA OF THE MANDIBULAR BUCCAL SHELF

Currently, miniscrews installed parallel to the roots are widely used in the practice of orthodontic treatment. When planning the placement of miniimplants, it is necessary to evaluate the anatomical factors that affect the stability of the miniscrew in the bone. For the analysis, we selected the zone of the external oblique line, where the thickness of bone tissue in the area of the first and second molars was estimated in the vertical and horizontal planes. As a result of the study, it was found that the area of the distal surface of the distal root of the second molar had the greatest thickness of bone tissue. An increase in the vestibular-oral thickness was also observed in the distal direction.

Changing trabecular patterns in panoramic radiographs of Swedish women during 25 years of follow-up

Objectives: The radiographic trabecular pattern on dental radiographs may be used to predict fractures. The aim of this study was to analyze longitudinal changes in the mandibles of 145 females between 1980 and 2005. Methods: Panoramic radiographs were obtained in 1980 and 2005. On 290 radiographs, regions of interest (ROIs) were selected in the ramus, angle and body. In all ROIs, the orientation was measured in 36 directions with the line frequency deviation method. The effects of ageing were analyzed for the fracture and the non-fracture groups separately. Results: During the follow-up, 61 females suffered fractures of the hip, wrist, spine, leg or arm. The fracture and non-fracture groups displayed dissimilar age changes in each investigated ROI. All significant changes pertained to increasing values of line frequency deviation. With increasing age, the trabecular network in the mandible lost details and the trabeculae became more aligned in their main direction. In the “ramus”, the alignment was to the 110–120˚ axis, parallel to the posterior and anterior ramus border. In the “angle”, the alignment was to the 135–150˚ axis, parallel to the oblique line, and in the “body” ROI to the 150–175˚ direction, approximately parallel to the occlusal plane and inferior cortex. Conclusion: Most changes were consistent with the notion that the bone aged less severely in the non-fracture group. In the fracture group, the findings indicate that bone loss leads to redistribution of the remaining bone tissue in such a way that the trabeculae are accentuated perpendicular to the principal loading.

VIRIATION OF THE EXTERNAL BRANCH OF THE SUPERIOR LARYNGEAL NERVE

Till now, there is no universal clinical classification about variations of the external branch of the superior laryngeal nerve despite the multiple classifications that was proposed. The aim of this research is identification and systematization of topographic types of the external branch of the superior laryngeal nerve. The study is based on the autopsy material (21 complexes organs of the neck) and on identification of variations of 40 external branches of the superior laryngeal nerve. We identify two permanent landmark that are located at the minimum distance from nerve and on which we made metrical calculations: oblique line of thyroid cartilage, tendinous arch of the inferior pharyngeal constrictor muscle. The “entry” point of the nerve is always located on the inferior pharyngeal constrictor muscle,and not protruding beyond the oblique line of thyroid cartilage superiorly and tendinous arch of the inferior pharyngeal constrictor muscle anteriorly. The proposed topographic classification of the location of the external branch of the superior laryngeal nerve is based on localization of point of pierced of the nerve relating to the length of the oblique line of thyroid cartilage. In 64.2% of cases, the external branch of the superior laryngeal nerve was in close proximity to the upper pole of the thyroid gland, which could lead to its damage during surgery (type I and II). In type III and IV (35.8%) - the point of "entry" in the muscle was located as far as possible from the upper pole of the thyroid gland, and most of the nerve was covered by the fibers of the inferior pharyngeal constrictor muscle.

Anatomical landmarks of the external branch of the superior laryngeal nerve

Background. The external branch of the superior laryngeal nerve innervates a cricothyroid muscle, which provides tension in vocal cords and formation of high-frequency sounds. When the nerve is damaged during surgery, patients may notice hoarseness, inability to utter high pitched sounds, “rapid fatigue” of the voice, and dysphagia. According to literature, paresis of an external branch of the superior laryngeal nerve reaches up to 58% after thyroid surgery. Aim: to identify permanent landmarks and topographic variations of the external branch of the superior laryngeal nerve. Materials and methods. The study is based on the autopsy material (21 complexes organs of the neck) and on identification of variations of 40 external branches of the superior laryngeal nerve. We identified two permanent landmarks that are located at the minimum distance from nerve and we made metrical calculations relative to them: oblique line of thyroid cartilage and tendinous arch of the inferior pharyngeal constrictor muscle. Results. The piercing point of the nerve is always located at the inferior pharyngeal constrictor muscle without protruding beyond the oblique line of thyroid cartilage superiorly and tendinous arch of the inferior pharyngeal constrictor muscle anteriorly. The nerve had the parallel direction in 92.8% of cases (angel less than 30 degrees) relative to the oblique line and in 85.7% cases it was in close proximity to this line (at distance up to 4 mm). The proposed topographic classification of the location of the external branch of the superior laryngeal nerve is based on localization of the piercing point of the nerve relative to the length of the oblique line of thyroid cartilage and the risk of nerve damage. In 14.2% of cases, the piercing point was in the front third of the line (type I), and in 50% it was in the middle third of this line (type II). These variations of the external branch of the superior laryngeal nerve was in close proximity to the upper pole of the thyroid gland, which could have lead to its damage during surgery. In type III and IV (35.8%) – the piercing point in the muscle was located as far as possible from the upper pole of the thyroid gland and the greater part of the nerve was covered with the fibers of inferior pharyngeal constrictor muscle. Conclusion. We identified the main orienteers for the search and proposed anatomical classification of the location of the external branch on the superior laryngeal nerve.