• Journal of the Korean Wood Science and Technology
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• v.49 no.6
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• pp.541-549
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• 2021

This paper reports a method to evaluate the residual strength of insect-damaged radiata pine lumber, such as the screw withdrawal strength as a semi-destructive method and a compression parallel to the grain test to assess the density changes after exposure to outdoor conditions. The screw withdrawal strength test was used as a semi-destructive method to estimate the residual density of decayed lumber. A compression parallel to the grain test was applied to evaluate the residual density. Three variables, such as the screw withdrawal strength, compression parallel to the grain, and residual density, were analyzed statistically to evaluate their relationships. The relationship between the residual density and screw withdrawal strength showed a good correlation, in which the screw withdrawal strength decreased with decreasing density. The other relationship between the residual density and compression parallel to the grain was also positively correlated; the compression parallel to the grain strength decreased with decreasing density. Finally, the correlation between the three variables was statistically significant, and the mutual correlation coefficients showed a strong correlation between the three variables. Hence, these variables are closely correlated. The test results showed that the screw withdrawal strength could be used as a semi-destructive method for an in situ estimation of an existing wood structure. Moreover, the method might approximate the residual density and compression parallel to the grain if supplemented with additional data.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.6
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• pp.452-457
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• 2016

Single screw compressors are widely used in the fields of air/gas compression, refrigeration, and chemical fluid transportation systems. A single-screw compressor is composed of a screw rotor and two gate rotors located at both sides. This simple construction enables low rotational speed of the rotor, efficient compression with low noise, low vibration, and long bearing life. Despite these merits, the design method of single-screw compressors is not well known. To accelerate the industrial application of single-screw compressors, a design method using coordinate transformation is presented in this paper, and a tool trajectory is established for machining. Finally, the screw rotor, which is machined using the proposed method, is presented.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1172-1175
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• 2004

At present, CHS(Compression Hip Screw) is one of the best prosthesis for the intertrochanteric fracture. There is nothing to evaluate the CHS itself with the finite element analysis and mechanical tests. They have same ways of the experimental test of the ASTM standards. The purpose of this study is to evaluate the existing CHS and the new CHS which have transformational design factors with finite element analysis and mechanical tests. The mechanical tests are divided into compression tests and fatigue test for evaluating the failure load, strength and fatigue life. This finite element method is same as the experimental test of the ASTM standards. Under 300N of compression load at the lag screw head. There are less differences between Group (5H, basic type) and Group which has 8 screw holes. However, there are lots of big differences between Group and Group which is reinforced about thickness of the neck range. Moreover, the comparison of Group and Group shows similar tendency of the comparison of Group and Group . The Group is reinforced the neck range from Group. After the experimental tests and the finite element analysis, the most effective design factor of the compression hip screws is the reinforcement of the thickness, even though, there are lots of design factors. Moreover, to unite the lag screw with the plate and to analyze by static analysis, the result of this method can be used with experimental test or instead of it.

• Journal of Korean Foot and Ankle Society
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• v.9 no.1
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• pp.52-58
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• 2005

Purpose: To analyze the overall clinical outcome, overall assessment, and patient's satisfaction rate of subtalar arthrodesis using the cannulated compression screw. Materials and Methods: This study is based on 17 patients, 17 feet who underwent subtalar arthrodesis using the cannulated compression screw from March, 1997 to March, 2004 with at least 1 year follow-up. The average follow-up period was 33.0 months (12 to 72 months). Functional results were assessed using the American Orthopaedic Foot and Ankle Society Ankle-Hindfoot (AOFAS) score, and Visual Analysis Scale (VAS) pain score, patients' returning to previous occupation and patients' satisfaction rate were also evaluated. Results: The mean AOFAS scores at final follow-up were 80.4 points (range $66{\sim}92$). The satisfactory rates were as follow. Thirteen patients (76.4%) were at least satisfied with surgical result at final follow-up. Patients' VAS pain score was average 2.8 points ($1{\sim}6$). Fourteen (82.3%) patients returned to previous job at mean postoperative period of 11.3 months (range 3-18 months). Patients' work efficiency after returning to previous occupation was 68.7% (range $33{\sim}100%$). There were 9 complications which were 3 cases of sural nerve injury, 1 case of valgus malunion, and 5 cases of the hindfoot residual pain. Conclusion: We obtained the satisfactory functional results with relatively high patient satisfaction rate of 76%. So we conclude that subtalar arthrodesis using the cannulated compression screw is a reliable method for addressing the painful end-stage subtalar osteoarthritis and unreconstructible comminuted calcaneal fractures. However we also found out that average 11 months were necessary for patients to return to their job.

• Journal of Korean Foot and Ankle Society
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• v.20 no.3
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• pp.131-134
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• 2016

Purpose: This study aimed to evaluate the outcomes, including the complications, of open reduction and internal fixation using a headless cannulated compression screw for a fifth metatarsal base fracture. Materials and Methods: We retrospectively investigated 11 patients with 5th metatarsal base fracture who were treated with a headless cannulated compression screw. The mean follow-up period was 13 months (8~15 months), and the mean age was 46.5 years (21~70 years). We analyzed the patients' sex, age, time to union, amount of fracture displacement, and complications. The American Orthopaedic Foot and Ankle Society (AOFAS) midfoot score was used for clinical assessment. Results: The average amount of displacement decreased significantly from 3.4 mm (2.1~5.2 mm), preoperatively, to 0.4 mm (0~1.3 mm), postoperatively (p<0.001). The average bone union time was 54.1 days (41~68 days). There were no complications, such as a metal failure, irritation, and loss of a reduction. The mean AOFAS midfoot score was 97.7 (90~100) at 6 months, postoperatively. Conclusion: We suggest that a headless cannulated compression screw for 5th metatarsal base fracture is a useful and alternative method for a firm fixation without complications.

• Journal of Korean Neurosurgical Society
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• v.61 no.2
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• pp.180-185
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• 2018

Objective : Many lumbosacral fixation techniques have been described to offer a more screw-bone purchase. The forward anatomical fixation parallel to the endplate is still the most preferred method. Literature revealed little knowledge regarding the mechanical stability of lumbosacral trans-endplate fixation compared to the traditional trans-pedicular screw fixation method. The aim of this study is to assess the pull-out strength of lumbosacral screws penetrating the end plate and comparing it to the conventional trans-pedicular screw insertion method. Methods : Eight lumbar and eight sacral vertebrae, with average age 69.4 years, Left pedicles of the 5th lumbar vertebrae were used for trans-endplate screw fixation, group 1A, right pedicles were used for anatomical trans-pedicular screw fixation, group 1B. In the sacral vertebrae, the right side S1 pedicles were used for trans-endplate fixation, group 2A, left side pedicles were used for anatomical trans-pedicular screw fixation, group 2B. The biomechanical tests were performed using the axial compression testing machine. All tests were applied using 2 mm/min traction speed. Results : The average pull-out strength values of groups 1A and 1B were $403.78{\pm}11.71N$ and $306.26{\pm}17.55N$, respectively. A statistical significance was detected with p=0.012. The average pull-out strength values of groups 2A and 2B were $388.73{\pm}17.03N$ and $299.84{\pm}17.52N$, respectively. A statistical significance was detected with p=0.012. Conclusion : The trans-endplate lumbosacral fixation method is a trustable fixation method with a stronger screw-bone purchase and offer a good alternative for surgeons specially in patients with osteoporosis.

• Journal of Korean Foot and Ankle Society
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• v.16 no.1
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• pp.38-46
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• 2012

Purpose: This study was performed retrospectively to evaluate clinical outcomes of distal metatarsal osteotomy using bio-compression screw as the joint preservation method for advanced hallux rigidus. Materials and Methods: Eleven cases were followed up for more than 1 year after distal metatarsal dorsal wedge osteotomy for advanced hallux rigidus. The clinical evaluation was performed according to the American Orthopaedic Foot and Ankle Society (AOFAS) score and patient's satisfaction score. The range of motion, and the period to return to running exercise, tip-toeing gait, squatting, walking down the stairs were evaluated. As the radiographic evaluation, the interval of $1^{st}$ MTP (metatarsophalangeal) joint space and the period to union were measured. Results: The AOFAS hallux score had improved significantly from preoperative average 50.7 points to 87.6 points at the last follow-up (p=0.005). The subjective satisfaction score was average 90.6 points. There were no case of subsequent fusion or additional operation, and no complication associated with bio-compression screw. The period to return to running exercise, tip-toeing gait, squatting, walking down the stairs were average of 24.8 weeks, 20.4 weeks, 16.8 weeks, 18.5 weeks respectively. Dorsiflexion of $1^{st}$ MTP joint had improved significantly from preoperative average $17.5^{\circ}$ to $44^{\circ}$ (p<0.001). All cases achieved union of osteotomy site, and the period to union was average 10.4 weeks. The interval of $1^{st}$ MTP joint space had improved significantly from preoperative average 1.2 mm to 3.5 mm (p=0.014). Conclusion: Distal metatarsal osteotomy using bio-compression screw seems to be one of effective treatment methods for advanced hallux rigidus, because of restoration of the first MTP joint motion, and reliable pain relief, and needlessness of hardware removal.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.11 no.1
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• pp.69-77
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• 1989

This is a retrospective study on 219 patients with mandibular fracture. The patients were treated in the Dept. of Oral Maxillofacial Surgery of WON KWANG UNIV. HOSPITAL from Aug. 1, 1984 to Sept. 30. 1988. The results were as follows. 1. The mandibular fractures occured most frequently in the twenties(35%) and male were predominant (74.7%) than females. 2. The most frequent etiologic factor was traffic accident(34.3%). 3. The most common location of fracture was symphysis(37.1%). And angle(27.6%), condyle(25.7%), ramus(1.6%) were next in order of frequency. 4. In mandible fracture, they have an average 1.8 fracture line. 5. The use of plate & screw system were more increased in the comparison of each year. 6. Intermaxillary fixation period was more reduced from the concept of 6 weeks fixation, due to the use of Plate & screw system. 7. Postoperative acute wound infection was developed 9.6% in 219 mandibular fracture patients. The compression osteosynthesis was most common cause of acute wound infection than any other treatment method. 8. Postoperative malocclusion was developed 4% in 219 mandibular fracture. And the compression osteosynthesis was most common cause of malocclusion. 9. Acute wound infection was detailed by the approach method. The Intraoral & extraoral combination method was most common cause on acute infection and intraoral, extraoral approach method was next in order of frequency. 10. Normal mouth opening process was proportioned to IMF period. The short IMF period have a fast normal mouth opening process.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.1
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• pp.72-78
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• 2004

In this paper, mechanical behaviors of developed pedicle screw system, made of bio-mechanical materials(Ti-6Al-4V, Grade 5), ale predicted using FEM analysis. As a first step, morphologic construction of normal Korean spines and surgical operation convenience are considered to design optimum pedicle screw system. In this step, various design variables are considered as design parameters to develop optimized models. As a next step, tension and bending tests are performed to improve the structural performance of the developed system using finite element method. In this step, required Static compression and bending test specifications by ASTM F-04 25 04 01 are applied to understand the bio-mechanical behaviors of the designed spinal implant system under various load types. As the results of this research, it is possible to develop efficient pedicle screw system, having enough rigidity and fixation to stand any spinal damage under allowable stress conditions.

• Journal of Biosystems Engineering
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• v.10 no.2
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• pp.47-54
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• 1985

Performance of a screw press was investigated experimentally with soybeans of various temperatures in order to find out a proper temperature of soybean to extract the oil by the mechanical method. Crude oil extracted by the screw press was chemically analyzed to determine a level of processing the oil for the oil to be used as a fuel for a compression ignition engine. The crude oil was degummed and dried by a plant type laboratory experimental setup to decide whether the processes are effective to improve quality of the oil as a fuel. The degummed oil and the degummed and dried oil were also chemically analyzed and were compared with the crude oil and the commercially degummed and dried soybean oil. The results are as follows: 1. In extraction of soybean oil by a screw press, heating soybeans is effective to increase oil production and to decrease energy consumption of the press. A proper temperature of soybean to extract the oil by the press was determined as about $50^{\circ}C$. 2. Soybean oil production and electric energy consumption of the press are about 83 ml and 58 Wh per 1 kg of soybeans heated to about $50^{\circ}C$, respectively. 3. The quality of crude oil produced by the press is similar to that of the commercially degummed and dried oil. The crude oil does not need to be degummed or dried for use as an engine fuel.