• Geomechanics and Engineering
• /
• v.15 no.5
• /
• pp.1113-1124
• /
• 2018

Geological dynamic hazards during deep coal mining are caused by the failure of a composite system consisting of the rock and coal layers, whereas the joint in coal affects the stability of the composite system. In this paper, the compression test simulations for the rock-coal combined body with single joint in coal were conducted using $PFC^{2D}$ software and especially the effects of joint length and joint angle on strength and failure characteristics in a rock-coal combined body were analyzed. The joint length and joint angle exhibit a deterioration effect on the strength and affect the failure modes. The deterioration effect of joint length of L on the strength can be neglected with a tiny variation at ${\alpha}$ of $0^{\circ}$ or $90^{\circ}$ between the loading direction and joint direction. While, the deterioration effect of L on strength are relatively large at ${\alpha}$ between $30^{\circ}$ and $60^{\circ}$. And the peak stress and peak strain decrease with the increase of L. Additionally, the deterioration effect of ${\alpha}$ on the strength becomes larger with the increase of L. With the increase of ${\alpha}$, the peak stress and peak strain first decrease and then increase, presenting "V-shaped" curves. And the peak stress and peak strain at ${\alpha}$ of $45^{\circ}$ are the smallest. Moreover, the failure mainly occurs within the coal and no apparent failure is observed for rock. At ${\alpha}$ between $30^{\circ}$ and $60^{\circ}$, the secondary shear cracks generated in or close to the joint tips, cause the structural instability failure of the combined body. Therefore, their failure models present as a shear failure along partial joint plane direction and partially cutting across the coal body or a shear failure along the joint plane direction. However, at ${\alpha}$ of $60^{\circ}$ and L of 10 mm, the "V-shaped" shear cracks cutting across the coal body cause its final failure. While crack nucleations at ${\alpha}$ of $0^{\circ}$ or $90^{\circ}$ are randomly distributed in the coal, the failure mode shows a V-shaped shear failure cutting across the coal body.

• Journal of Chest Surgery
• /
• v.8 no.1
• /
• pp.37-44
• /
• 1975

Authors have reviewed the records of seven patients of multiple rib fractures with severe flail chest who were admitted to Hanyang University Hospital during the 3 years period from 1972 through 1975. Of the seven patients studied, automobile accidents led to the injuries in 4 cases, two patients were injured in fall from a tree and on the ox-heading. All who had a blunt trauma without any open wound on the chest. The numbers of the fractured ribs accounted for 6 to 9 of the ribs including double fractures from 3 to 5 ribs. The left side fractures occurred in the 6 patients and in the right only one patient. Thus the flail segment was more often located in the left antero-lateral position than in the right lateral position [the ratio was 6:1].. All cases had associated injuries. The injuries and multiple fractures were the most common associated injuries occurring in four and five of the patients respectively. The patients were classified as having associated head injuries when they were admitted in comatose or semicomatose state. When a major degree of instability of the thoracic cage exists, adequate respiratory change is not possible. For this reason the tracheostomy was performed in five patients in an acutely injured patient with flail chest only after an endotracheal tube has been inserted or after an endotracheal suction. All patients had secondary complications in the pleural cavity, such as hemothorax or hemopneumothorax with or without intrapulmonary hemorrhage and subcutaneous emphysema. Therefore, closed thoracostomy was performed in five patients in the emergency room. The thoracotomy was required in four patients: immediate operation without closed thoracostomy was performed in two patients and the thoracotomy was indicated in two patients after closed thoracostomy, because of increasing intrathoracic hemorrhage. As to the fixation of the flail segments, authors employed two techniques; one was towel clip traction of the flail segments and the other was intramedullary insertion of Kirschner`s wire in to the double fractured rib fragments for the fixation of the flail segments [Kirschner`s wire fixation]. Because` of an different results in the course of treatment between two techniques, data from patients with towel clip traction was compared with those from patients with thoracotomy and Kirschner`s wire fixation of the flail segments. Of the three patients with towel clip traction, two patients required bronchoscopic toilet due to lung atelectasis which developed because of inadequate motion of thoracic cage and poor expectoration. This was in contrast to the four patients with thoracotomy and Kirschner`s wire fixation, who didn`t these complication because of adequate motion of the thoracic cage and subsequent good expectoration.

• 한국문화재보존과학회:학술대회논문집
• /
• 2004.10a
• /
• pp.92-100
• /
• 2004

The host rocks of brick-shaped stone pagoda in the Bunhwangsa temple are lots of kinds andesitic rocks, which has gone through mechanical and chemical weathering. As the overall observation, the pagoda is serious damages by air pollutants, and the northeast parts show the much advanced state of turning white, while the southeast parts are heavily cracked in the materials. The rocks of brick-shaped pagoda body are in a relatively stable condition of weathering and damage except for the abrasion and cracks of the corners. The rocks of the pagoda roof suffer from more symptoms including multiple peel-offs, exfoliation, cracks forming round lines, and falling off stone pieces. The pagoda roof rocks are dominated by the thriving leafy lichens and mosses, especially, there are higher plants (selaginella involvens, dandelions) taking root actively between the brick stones and content mortar. There are even light gray precipitates like stalactites between the rocks of the body, In particular, the 1st and 2nd floor in the east side and the body parts in the north side are the most serious. Their major minerals are calcite, gypsum and clay minerals. The rocks of the stylobate and the tabernacle in all the four directions are composed mainly of granitic rocks. The materials consisting of the tabernacles show the severe splits and distortion, which causes the structural instability. The stylobate rocks are heavily contaminated by some weeds with the often marks of inorganic contamination by secondary hydroxides. The central part of the east stylobate has been sinking, while that of the 1st floor west stylobate is protruded nesting a line of cracks. Accordingly, the inside of the tabernacle is always humid with the constant introduction of rainwater. The stone lion standing in the southeast and northeast side are alkali granite, while that in the southwest and northwest lithic tuff. Each of the stone lion also coated with various colored lichens, mosses, algae, bacteria and bryophyte. The external materials of the pagoda have deteriorated the functions of the rocks and made the loss, falling off, and biological contamination even worse due to the surface weathering. Thus it's urgent to come up with scientific restoration and conservation measures through clinical tests.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.18 no.3
• /
• pp.227-243
• /
• 2005

This paper presents a hybrid control system combining lead rubber bearings and hydraulic actuators for seismic response control of a cable stayed bridge. Because multiple control devices are operating, a hybrid control system could improve the control performances. However, the overall system robustness may be impacted negatively by additional active control devices. Therefore, a secondary on-off type controller according to the responses of lead rubber bearings is combined with LQG algorithm to improve the controller robustness. Numerical simulation results show that control performances of the hybrid system controlled by an on off type LQG algorithm are improved compared to those of the passive and active control systems and are similar to those of performance oriented hybrid system controlled by a LQG algorithm with the similar peak and normed control forces. Furthermore, it is verified that the hybrid system with an on-off type LQG controller is more robust for stiffness matrix perturbation than conventional hybrid control of system, and there are no signs of instability in the overall system. The proposed control system also maintains the control performance under not only the design earthquakes but also the other earthquakes. Therefore, the hybrid control system using on-off type LQG algorithm could be proposed as an improved control strategy for seismically excited cable-stayed bridges containing many uncertainties.

• Clinics in Shoulder and Elbow
• /
• v.14 no.1
• /
• pp.20-26
• /
• 2011

Purpose: The purpose of this study is to investigate the accompanying lesions of humerus greater tuberosity fracture with anterior shoulder dislocation and to analyze its clinical results. Materials and Methods: From May 2005 to November 2008, arthroscopy was performed on a total of 30 selected patients who were diagnosed with humerus greater tuberosity fracture with anterior shoulder dislocation and who were also under the age of 40. The preoperative and postoperative Constant and Rowe scores were compared. Results: There was a total of 21 cases of anteroinferior labral lesions: 2 Bankart lesions, 4 bony Bankart lesions, 4 Perthes lesions, 2 free ALPSA lesions, 3 GLAD lesions and 6 capsular tears. For other lesions, 5 rotator cuff partial tears, 3 SLAP lesions and 1 biceps tendon rupture were found. The constant scores were increased from 56.3 to 94.43 points (p=0.034), and the Rowe scores were increased from 52.56 to 91.76 points (p=0.026). Conclusion: For humerus greater tuberosity fracture with anterior shoulder dislocation, the accompanying lesion was identified and the fracture was treated using arthroscopy. Good clinical results and bone union were achieved. According to the secondary arthroscopic findings, all of the Perthes lesion, the free ALPSA lesion, the GLAD lesion and the capsular tear spontaneously healed or they did not progress to extended rupture although arthroscopic suture was not performed. Any postoperative secondary instability was not observed.

• Journal of the Korean Orthopaedic Association
• /
• v.55 no.4
• /
• pp.281-293
• /
• 2020

An anterior cruciate ligament (ACL) reconstruction is one of the most frequent surgical procedures in the knee joint, but despite the better understanding of anatomy and biomechanics, surgical reconstruction procedures still fail to restore rotational stability in 7%-16% of patients. Hence, many studies have attempted to identify the factors for rotational laxity, including the anterolateral ligament (ALL), but still showed controversies. Descriptions of the ALL anatomy are also confused by overlapping nomenclature, but it is usually known as a distinctive fiber running in an anteroinferior and oblique direction from the lateral epicondyle of the femur to the proximal anterolateral tibia, between the fibular head and Gerdy's tubercle. The importance of the ALL as a secondary restraint in the knee has been emphasized for successful ACL reconstructions that can restore rotational stability, but there is still some controversy. Some studies reported that the ALL could be a restraint to the tibial rotation, but not to anterior tibial translation. On the other hand, some studies reported that the role of ALL in rotational stability would be limited as a secondary structure because it bears loads only beyond normal biomechanical motion. The diagnosis of an ALL injury can be performed by a physical examination, radiology examination, and magnetic resonance imaging, but it should be assessed using a multimodal approach. Recently, ALL was considered one of the anterolateral complex structures, as well as the Kaplan fiber in the iliotibial band. Many studies have introduced many indications and treatment options, but there is still some debate. The treatment methods are introduced mainly as ALL reconstructions or lateral extra-articular tenodesis, which can achieve additional benefit to the knee stability. Further studies will be needed on the indications and proper surgical methods of ALL treatment.

• Journal of Yeungnam Medical Science
• /
• v.8 no.2
• /
• pp.128-137
• /
• 1991

Peritoneal dialysis has been widely considered to be the dialytic treatment of choice for acute renal failure in infants and young children, because the technique is simple, safe and easily adapted for these patients. Also peritoneal dialysis in infants might have more effective ultrafiltration and clearance than in adults. In certain circumstances associated with hemodynamic instability, ordinary volume peritoneal dialysis(30-50 ml/kg body weight per exchange) or hemodialysis may not be suitable unfortunately. But frequent cycled, low volume, high concentration peritoneal dialysis may be more available to manage the hemodynamically untable acute renal failure of newborns and infants. Seven infants underwent peritoneal dialysis for hemodynamically unstable acute renal failure with low exchange volume($14.2{\pm}4.2ml/kg$), short exchange time(30 to 45 minutes) and hypertonic glucose solution(4.25% dextrose). Age was $1.9{\pm}1.3$ months and body weight was $4.6{\pm}1.6kg $. Etiology of acute renal failure was secondary to sepsis with or without shock(5 cases) and postcardiac operation(2 cases). Catheter was inserted percutaneously with pigtail catheter or Tenkhoff catheter by Seldinger method. Dialysate was commercially obtained Peritosol which contained sodium, chloride, potassium, magnesium, lactate and calcium. Net ultrafiltration(ml/min) showed no difference between low volume dialysis and control($0.27{\pm}0.09$ versus $0.29{\pm}0.09$) Blood BUN decreased from $95.7{\pm}37.5$ to $75.7{\pm}25.9mg/dl$ and blood pH increased from $7.122{\pm}0.048$ to $7.326{\pm}0.063$ after 24 hours of peritoneal dialysis. We experienced hyperglycemia which were controlled by insulin(2 episodes), leakage at the exit site(2), mild hyponatremia(1) and Escherichia coli peritonitis(1). Two children of low volume dialysis died despite the treatment. In our experience, low volume and high concentration peritoneal dialysis with frequent exchange may have sufficient ultrafiltration and clearance without significant complications in the certain risked acute renal failure of infants.

• Korean Journal of Heritage: History & Science
• /
• v.55 no.2
• /
• pp.200-211
• /
• 2022

The celadon stools with an openwork ring design which consist of four items as one collection were excavated from Gaeseong, Gyeonggi-do Province. The celadon stools were designated and managed as treasures due to their high arthistorical value in the form of demonstrating the excellence of celadon manufacturing techniques and the fanciful lifestyles during the Goryeo Dynasty. However, one of the items, which appeared to have been repaired and restored in the past, suffered a decline in aesthetic value due to the aging of the treatment materials and the lack of skill on the part of the conservator, raising the need for re-treatment as a result of structural instability. An examination of the conservation condition prior to conservation treatment found structural vulnerabilities because physical damage had been artificially inflicted throughout the area that was rendered defective at the time of manufacturing. The bonded surfaces for the cracked areas and detached fragments did not fit, and these areas and fragments had deteriorated because the adhesive trickled down onto the celadon surface or secondary contaminants, such as dust, were on the adhesive surface. The study identified the position, scope, and conditions of the bonded areas at the cracks UV rays and microscopy in order to investigate the condition of repair and restoration. By conducting Fourier-transform infrared spectroscopy(FT-IR) and portable x-ray fluorescence spectroscopy on the materials used for the former conservation treatment, the study confirmed the use of cellulose resins and epoxy resins as adhesives. Furthermore, the analysis revealed the addition of gypsum(CaSO₄·2H₂O) and bone meal(Ca₁₀ (PO₄)₆(OH)₂) to the adhesive to increase the bonding strength of some of the bonded areas that sustained force. Based on the results of the investigation, the conservation treatment for the artifact would focus on completely dismantling the existing bonded areas and then consolidating vulnerable areas through bonding and restoration. After removing and dismantling the prior adhesive used, the celadon stool was separated into 6 large fragments including the top and bottom, the curved legs, and some of the ring design. After dismantling, the remaining adhesive and contaminants were chemically and physically removed, and a steam cleaner was used to clean the fractured surfaces to increase the bonding efficacy of the re-bonding. The bonding of the artifact involved applying the adhesive differently depending on the bonding area and size. The cyanoacrylate resin Loctite 401 was used on the bonding area that held the positions of the fragments, while the acrylic resin Paraloid B-72 20%(in xylene) was treated on cross sections for reversibility in the areas that provided structural stability before bonding the fragments using the epoxy resin Epo-tek 301-2. For areas that would sustain force, as in the top and bottom, kaolin was added to Epo-tek 301-2 in order to reinforce the bonding strength. For the missing parts of the ring design where a continuous pattern could be assumed, a frame was made using SN-sheets, and the ring design was then modeled and restored by connecting the damaged cross section with Wood epos. Other restoration areas that occurred during bonding were treated by being filled with Wood epos for aesthetic and structural stabilization. Restored and filled areas were color-matched to avoid the feeling of disharmony from differences of texture in case of exhibitions in the future. The investigation and treatment process involving a variety of scientific technology was systematically documented so as to be utilized as basic data for the conservation and maintenance.