• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.1992-2007
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• 1997

A new algorithm for planning a collision-free path is developed based on linear prametric curve. In this paper robot is assumed to a point, and two linear parametric curve is used to construct a path connecting start and goal point, in which single intermediate connection point between start and goal point is considered. The intermediate connection point is set in polar coordinate(${\theta}{\delta}$) , and the interference between path and obstacle is mapped into CPS(connection point space), which is defined a CWS GM(circular work space geometry mapping). GM of all obstacles in workspace creates overlapping images of obstacle in CPS(Connection Point Space). The GM for all obstacles produces overlapping images of obstacle in CPS. The empty area of CPS that is not occupied by obstacle images represents collision-free paths in Euclidian Space. A GM based on connection point in elliptic coordinate(${\theta}{\delta}$) is also developed in that the total length of path is depend only on the variable .delta.. Hence in EWS GM(elliptic work space geometry mapping), increasing .delta. and finding the value of .delta. for collision-free path, the shortest path can be searched without carring out whole GM. The GM of obstacles expersses all possible collision-free path as empty spaces in CPS. If there is no empty space available in CPS, it indicates that path planning is not possible with given number of connection points, i.e. path planning is failed, and it is necessary to increase the number of connection point. A general case collision-free path planning is possible by appling GM to configuration space obstacles. Simulation of GM of obstacles in Euclidian space is carried out to measure performance of algorithm and the resulting obstacle images are reported.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.9 s.252
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• pp.921-928
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• 2006

Wake-induced boundary-layer transition on a NACA0012 airfoil with zero angle of attack is experimentally investigated in periodically passing wakes under the moderate level of free-stream turbulence. The periodic wakes are generated by rotating circular cylinders clockwise or counterclockwise around the airfoil. The free-stream turbulence is produced by a grid upstream of the rotating cylinder, and its intensities $(Tu_{\infty})$ at the leading edge of the airfoil are 0.5 and 3.5%, respectively. The Reynolds number (Rec) based on chord length (C) of the airfoil is $2.0{\times}10^5$, and Strouhal number (Stc) of the passing wake is about 1.4. Time- and phase-averaged streamwise mean velocities and turbulence fluctuations are measured with a single hot-wire probe, and especially, the corresponding wall skin friction is evaluated using a computational Preston tube method. The patch under the high free-stream turbulence $(Tu_{\infty}=3.5%)$ grows more greatly in laminar-like regions compared with that under the low turbulence $(Tu_{\infty}=0.5%)$ in laminar regions. The former, however, does not greatly change the turbulence level in very near-wall region while the latter does it. At further downstream, the former interacts vigorously with high environmental turbulence inside the pre-existing transitional boundary layer and gradually loses its identification, whereas the latter keeps growing in the laminar boundary layer. The calmed region is more clearly observed under the lower free-stream turbulence level and with the receding wakes.

• Archives of Reconstructive Microsurgery
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• v.8 no.2
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• pp.139-148
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• 1999

Since Nakayama's first report about venous flap, many experimental and clinical studies were done about this new type of flap. And due to its various benefits, its applications as arterialized venous free flap type have increased recently. In this study we have attempted to reconstruct composite of defects of the hand with new modification of arterialized venous free flap and simultaneous reconstruction of skin, nerve, tendon were performed successfully. From 1994 to 1999, the defects of the hands in 35 patients were reconstructed with various modifications of arterialized venous free flaps. The range of age was from 19 to 55 years and size of flap ranged from $1{\times}2cm\;to\;14{\times}9cm$. Among them, 12 cases of flap over 20cm in size were included. Indications of flaps were as follows: resurfacing of the defects of the skin (9 cases), simultaneous reconstruction of extensor, skin and digital nerve(2 cases), reconstruction of the skin with extensor(5 cases), as a flap-through type vascular reconstruction(6 cases), for digital nerve reconstruction(2 cases), contracture release(3 cases), and finger tip reconstruction(9 cases). All of the cases except one survived with marginal skin necrosis less than 10%. And relatively large flaps over 20cm in size successfully survived without any delay procedures. Composite reconstructions including tendon and nerve were successful with new modifications of this flap. Arterialized venous free flap is one of the useful procedure in reconstruction of the hand because it has many advantages such as non-bulky and good quality of flap, variable length of pedicle, preservation of major vascular pedicle, less operation time, single operative field and in addition possibility of various modifications.

• Advances in concrete construction
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• v.16 no.6
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• pp.277-290
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• 2023

In order to study the mechanical properties of basalt fiber reinforced ultra-fine fly ash concrete (BFUFARC), the effects of ultra-fine fly ash (UFA) content, basalt fiber content, basalt fiber length and water reducing agent content on the compressive strength, splitting tensile strength and flexural strength of the composite material were studied through experimental and theoretical analysis. Also, a scanning electron microscope (SEM) was employed to analyze the mesoscopic structure in the fracture surface of composite material specimens at magnifications of 500 and 3500. Besides, the energy release rate (G_c) and surface free energy (γ_s) of crack tip cracking on BFUFARC in different basalt fiber content were studied from the perspective of fracture mechanics. Further, the cracking resistance, reinforcement, and toughening mechanisms of basalt fibers on concrete substrate were revealed by surface free energy of BFUFARC. The experimental results indicated that basalt fiber content is the main influence factor on the splitting tensile strength of BFUFARC. In case that fiber content increased from 0 to 0.3%, the concrete surface free energy at the tip of single-sided crack showed a trend of increased at first and then decreased. The surface free energy reached at maximum, about 3.59 × 10^-5 MN/m. During the process of increasing fiber content from 0 to 0.1%, G_C-2_γS showed a gradually decreasing trend. As a result, an appropriate amount of basalt fiber can play a preventing cracking role by increasing the concrete surface free energy, further effectively improve the concrete splitting tensile performance.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.6
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• pp.688-696
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• 2023

In the present study, free roll decay and resistance performances of fishing vessels were evaluated with the combinations and variations of in the parameters of appendages which are attached to improve motion performance of fishing vessels. Computational Ffluid Ddynamics was used to perform free roll decay and resistance analysis. The roll period and decay coefficient were derived by the variations in the combination and dimensions of the primary appendages of the bilge keel and the under keel. It was observed thatThe variations of in the length of the under keel did not significantly impact to the roll damping coefficient. Conversely, for the bilge keel, an increase in the length and angle resulted in an increase in the roll damping coefficient. Comparison of resistance performance was additionally assessed among the selected hulls with the appendages and bare hull. The resistance of the hull with the appendages was higher than that of the bare hull due owing to the changes of in the pressure on the surface of the hull and trim angle. Throughout the present study, the impact of appendage parameter and arrangement on the free roll decay and resistance performance of fishing vessels were was assessed,. which This will be beneficial for the application of appendages to fishing vessels.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.27 no.6
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• pp.526-534
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• 2001

Purpose : The objective of this study is to ascertain whether the positive exists among the frenum length, the tongue movement and the speech and to present the normal range of tongue movement and guidelines for the choice of surgery, observation if necessary. Materials and Methods : 180 patients were evaluated. We divided 180 patients into 6 group by age. Each group was separated as follows; the age of 2.5-4, 5-6, 7-9, 10-12, 16-18. We measured the frenal length, the range of tongue motion and evaluated the speech so that we really questioned about the positive relationship between the tongue-tie and speech. We let the patient exercise the protrusive both(right, left) laterotrusive superior movement of the tongue. During these movements, we measured the distance between the vermilion border and the tongue tip. We also measured the distance from the tongue tip to the point contacting the upper lip with dorsum of the tongue during the maximal protrusive movement of the tongue. Three linear measurement of the anterior, inferior segment of the tongue including the lingual frenum, are made. These measurements are as follows: 1. Distance A. Free anterior portion of the tongue from the point of frenular insertion to the tongue tip. 2. Distance B. The distance from the initiating point of the lingual frenum to the point connecting the two sublingual carundcles to the lingual frenum perpendicularly. 3. Distance C. The distance from the point contacting the line crossing the sublingual caruncles with the lingual frenum to the terminating point of the lingual frenum. We transform three linear measures into a statistical ratio, A/(A-B+C), representing the length of the free portion of the tongue compared with the total sublingual dimensions. In addition, we assessed the speech through Picture Consonant Articulation Test(PCAT) and tried to find out the relationship between the length of the lingual frenum and speech. Conclusion : As people are born, they have small and restricted tongue. As people grow old, tongue motions are more liberate, and unrestricted and they can speak so freely. Therefore we suggest that until age 5, oral and maxillofacial surgeons postpone the surgery if not urgent, evaluate the maximal lingual motions and PCAT according to this article and observe their changes.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.5
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• pp.642-648
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• 1999

The digestive tract of the black sea bream, Acanthopagrus schlegeli is composed of esophagus, stomach, intestine, anus and four or five pyloric caeca. Pyloric caecum is a blind sac in shape and originated from pyloric portion of the stomach. Relative length of But (RLG), that is length of digestive tract to standard length, is 1.04 (n=10). Histological layer of the digestive tract is composed of serous membrane, muscular layer, undeveloped submucosal layer and mucosal layer. The mucosal folds of the esophagus are regular branched form, Esophageal muscularis mucosae is well-developed. Mucosal epithelial layer is composed of cuboidal or columnar epithelium and mucous secretory cell. Microvilli are absent in the free surface of mucosal epithelium. The mucosal folds of the stomach are regular unbranched form. The stomach has a well-developed muscular layer and muscularis mucosae. Microvilli are present in the free surface of mucosal surface epithelium. The fundic portion of the stomach have a well-developed gastric gland and more numerous secretory granules than the other parts. The mucosal folds of the pyloric caeca and the intestine are irregular branched form, Intestine is divided into the anterior, mid and posterior intestines with length of mucosal folds and histological features, Posterior intestine has a more developed striated border and goblet cells than the other parts. Mid intestine has a more abundant absorptive cells than the other parts in the intestine and pyloric caeca.

• Archives of Reconstructive Microsurgery
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• v.5 no.1
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• pp.24-34
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• 1996

There are many kinds of free flaps for management of extensive soft tissue defect of extremities in orthopaedic field. Free vascularized scapular flap is one of the most useful and relatively easy to application. This flap has been utilize clinically from early eighties by many microsurgical pioneers. Authors performed 102 cases of this flap from 1984 to 1995. We have to consider about the surgical anatomy of the flap, technique of the donor harvesting procedures, vascular varieties and anatomical abnormalities and success rate and the weak points of the procedure. This flap nourished by cutaneous branches from circumflex scapular vessels emerges from the lateral aspect of the subscapular artery 2.5-5cm from its lateral origin passing through the triangular space(bounded by subscapularis, teres minor, teres major, long head of triceps). The terminal cutaneous branch runs posteriorly around the lateral border of the scapular and divided into two major branches, those transeverse horizontally and obliquely to the fascial plane of overlying skin of the scapular body. We can utilize these arteries for scapular and parascapular flap. The vascular pedicle ranged from 5 to 10 cm long depends on the dissection, usually two venae comitantes accompanied circumflex scapular artery and its major branches. The diameter of the circumflex scapular artery is more than 1mm in adult, rare vascular variation. Surgical techniques : The scapular flap can be dissected conveniently with prone or lateral decubitus position, prone position is more easier in my experience. There are two kinds of surgical approaches, most of the surgeon prefer elevation of the flap from its outer border towards its base which known easier and quicker, but I prefer elevation of the flap from its outer border because of the lowering the possibilities of damage to vasculature in the flap itself which runs just underneath the subcutaneous tissue of the flap and provide more quicker elevation of the flap with blunt finger dissection after secure pedicle dissection and confirmed the course from the base of the pedicle. There are minimal donor site morbidity with direct skin closure if the flap size is not so larger than 10cm width. This flap has versatility in the design of the flap shape and size, if we need more longer and larger one, we can use parascapular flap or both. Even more, the flap can be used with latissimus dorsi musculocutaneous flap and serratus anterior flap which have common vascular pedicle from subscapular artery, some instance can combined with osteocutaneous flap if we include the lateral border of the scapular bone or parts of the ribs with serratus anterior. The most important shortcoming of the scapular free flap is non sensating, there are no reasonable sensory nerves to the flap to anastomose with recipient site nerve. Results : Among our 102 cases, overall success rate was 89%, most of the causes of the failure was recipient site vascular problems such as damaged recipient arterial conditions, and there were two cases of vascular anomalies in our series. Patients ages from 3 years old to 62 years old. Six cases of combined flap with latissimus dorsi, 4 cases of osteocutaneous flap for bone reconstruction, 62 parascapular flap was performed - we prefer parascapular flap to scapular. Statistical analysis of the size of the flap has less meaningful because of the flap has great versatility in size. In the length of the pedicle depends on the recipient site condition, we can adjust the pedicle length. The longest vascular pedicle was 14 cm in length from the axillary artery to the enter point cutaneous tissue. In conclusion, scapular free flap is one of the most useful modalities to manage the large intractable soft tissue defect. It has almost constant vascular pedicle with rare anatomical variation, easy to dissect great versatility in size and shape, low donor morbidity, thin and hairless skin.

• Journal of Mechanical Science and Technology
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• v.15 no.4
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• pp.465-472
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• 2001

A numerical study is carried out to clarify the characteristics of flow fields and breaking phenomena around a high speed catamaran hull advancing on calm water. Computations are carried out for Froude numbers between 0.2 and 1.0 and for ratios of the distance between hulls to the catamaran length varying between 0.2 and 0.5 for a mathematically defined Wigley hull. A Navier-Stokes solver which includes the nonlinearities of free surface conditions is employed. Computations are performed in a rectangular grid system based on the Marker & Cell method. For validation, present computation results are compared with existing experimental results. As an application, the results of the displacement catamaran are used for the breaking analysis.

• Structural Engineering and Mechanics
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• v.60 no.3
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• pp.455-470
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• 2016

In this paper, we investigate the free vibration of axially loaded non-uniform Rayleigh cantilever beams. The Rayleigh beams account for the rotary inertia effect which is ignored in Euler-Bernoulli beam theory. Using an inverse problem approach we show, that for certain polynomial variations of the mass per unit length and the flexural stiffness, there exists a fundamental closed form solution to the fourth order governing differential equation for Rayleigh beams. The derived property variation can serve as test functions for numerical methods. For the rotating beam case, the results have been compared with those derived using the Euler-Bernoulli beam theory.