• International Journal of Highway Engineering
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• v.13 no.3
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• pp.21-30
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• 2011

As well known, dowel bars are used to transfer traffic load acting on one edge to another edge of concrete slab in concrete pavement system. The dowel bars widely used in South Korea are round shape steel bar and they shows satisfactory performance under bending stress which is developed by repetitive traffic loading and environment loading. However, they are not invulnerable to erosion that may be caused by moisture from masonry joint or bottom of the pavement system. Especially, the erosion could rapidly progress with saline to prevent frost of snow in winter time. The problem under this circumstance is that the erosion not only drops strength of the steel dower bar but also comes with volume expansion of the steel dowel bar which can reduce load transferring efficiency of the steel dowel bar. To avoid this erosion problem in reasonable expenses, dowers bars with various materials are being developed. Fiber reinforced plastic(FRP) dower that is presented in this paper is suggested as an alternative of the steel dowel bar and it shows competitive resistance against erosion and tensile stress. The FRP dowel bar is developed in tube shape and is filled with high strength no shrinkage. Several slab thickness designs with the FRP dowel bars are performed by evaluating bearing stress between the dowel bar and concrete slab. To calculated the bearing stresses, theoretical formulation and finite element method(FEM) are utilized with material properties measured from laboratory tests. The results show that both FRP tube dowel bars with diameters of 32mm and 40mm satisfy bearing stress requirement for dowel bars. Also, with consideration that lean concrete is typical material to support concrete slab in South Korea, which means low load transfer efficiency and, therefore, low bearing stress, the FRP tube dowel bar can be used as a replacement of round shape steel bar.

• Journal of Chest Surgery
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• v.43 no.6
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• pp.602-613
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• 2010

Background: As life expectancy has been increased, the cardiac valve disease has been increased. In past, mechanical valve for valve replacement surgery was used widely, but it has many weaknesses, such as hemorrhage, teratogenic effect caused by warfarin, acute mechanical failure, taking warfarin during life, etc. So, the tissue valve is used widely and researches for durability of tissue valve are in progress. Tissue valves being used are all imported in Korea, and there is a lack of information on its geometry and design. So, we studied the geometry of porcine aortic and pulmonary valve, and tried to suggest theoretical basis for making the aortic and pulmonary valve. Material and Method: We harvested aortic and pulmonary valves of 25 pigs and measured the geometry of valve at fresh and glutaraldehyde (GA) fixed state. In each group, we measured the diameter of the base, diameter of commissure, valve height, commissural height, etc. Also, for making implantable porcine and bovine pericardial valve, we designed the valve stent form, thickness, height, and leaflet size, form, thickness by different size of valve. Result: The aortic and pulmonary valve geometry and ratio were measured in each group. The right coronary cusp of aortic valve and right facing cusp of pulmonary valve was bigger than other cusps and non coronary cusp was smaller than others (RCC: NCC : LCC=1 : 0.88 : 1). Valve height was correlated to the leaflet size. We designed the outer diameter of stented porcine aortic valve from 19 mm to 33 mm and designed stent height and width, using previous measured ratio of each structure, stent thickness, working thickness (for making valve). Also, we designed the size of stent and form for stented bovine pericardial valve, considering diameter of valve, leaflet length, height and leaflet minimum coaptation area. Conclusion: By measuring of 25 pig's aortic and pulmonary valve geometry and ratio, we can make theoretical basis for making implantable stented porcine valve and bovine pericardial valve in various size. After making implantable valve using these data, it is necessary to do in vivo and in vitro researches, furthermore.

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.6
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• pp.823-829
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• 2016

Eight Holstein steers ($216{\pm}48kg$ body weight) fitted with ruminal and duodenal cannulas were used to evaluate effects of wheat straw processing (ground vs pelleted) at two straw inclusion rates (7% and 14%; dry matter basis) in dry rolled or steam-flaked corn-based finishing diets on characteristics of digestion. The experimental design was a split plot consisting of two simultaneous $4{\times}4$ Latin squares. Increasing straw level reduced ruminal (p<0.01) and total tract (p = 0.03) organic matter (OM) digestion. As expected, increasing wheat straw level from 7% to 14% decreased (p<0.05) ruminal and total tract digestion of OM. Digestion of neutral detergent fiber (NDF) and starch, per se, were not affected (p>0.10) by wheat straw level. Likewise, straw level did not influence ruminal acetate and propionate molar proportions or estimated methane production (p>0.10). Pelleting straw did not affect ($p{\geq}0.48$) ruminal digestion of OM, NDF, and starch, or microbial efficiency. Ruminal feed N digestion was greater (7.4%; p = 0.02) for ground than for pelleted wheat straw diets. Although ruminal starch digestion was not affected by straw processing, post-ruminal (p<0.01), and total-tract starch (p = 0.05) digestion were greater for ground than for pelleted wheat straw diets, resulting in a tendency for increased post-ruminal (p = 0.06) and total tract (p = 0.07) OM digestion. Pelleting wheat straw decreased (p<0.01) ruminal pH, although ruminal volatile fatty acids (VFA) concentration and estimated methane were not affected ($p{\geq}0.27$). Ruminal digestion of OM and starch, and post-ruminal and total tract digestion of OM, starch and N were greater (p<0.01) for steam-flaked than for dry rolled corn-based diets. Ruminal NDF digestion was greater (p = 0.02) for dry rolled than for steam-flaked corn, although total tract NDF digestion was unaffected (p = 0.94). Ruminal microbial efficiency and ruminal degradation of feed N were not affected (p>0.14) by corn processing. However, microbial N flow to the small intestine and ruminal N efficiency (non-ammonia N flow to the small intestine/N intake) were greater (p<0.01) for steam-flaked than for dry rolled corn-based diets. Ruminal pH and total VFA concentration were not affected ($p{\geq}0.16$) by corn processing method. Compared with dry rolled corn, steam-flaked corn-based diets resulted in decreased acetate:propionate molar ratio (p = 0.02). It is concluded that at 7% or 14% straw inclusion rate, changes in physical characteristics of wheat straw brought about by pelleting negatively impact OM digestion of both steam-flaked and dry-rolled corn-based finishing diets. This effect is due to decreased post-ruminal starch digestion. Replacement of ground straw with pelleted straw also may decrease ruminal pH.

• Journal of Animal Science and Technology
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• v.44 no.2
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• pp.221-232
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• 2002

This study was conducted to investigate the effects of deficiency of essential amino acid in diet on feed intake and concentrations of free amino acid in plasma and brain(prepyriform cortex, PPC), and thereby to know the brain area engaged in the mechanism of feed intake regulation. In all trials, experimental diets were formulated with pure amino acid mixture to level of 15% nitrogen. Rats were trained to eat a single meal for 6 hours daily(meal feeding, 17:00-21:00). Feed intake and body weight were measured hourly on and after 7th day of feeding. In Exp. 1, feed intake and body weight were measured every hour, and the free amino acid concentrations of plasma and PPC were analysed at 0, 1, 2, 3 and 6 h on the 11th day of feeding. In Exp. 2, the complete diet was replaced with lysine devoid diet at the 11th day, and feed intake, body weight and free amino acid concentrations in plasma and PPC were samely measured on Exp. 1. In Exp. 1, feed intake on complete diet was self-sufficiented to daily feed intake level(15g/day) from the 7th day. Free amino acid concentrations of plasma and PPC at the 11th day were plateau at 1 hour after feeding. In Exp. 2, feed intake was quickly reduced by the diet replacement(P$<$0.05), and the free lysine concentration of plasma and PPC was also significantly decreased at 2 hour after feeding. However, cumulative feed intake was significantly decreased at 4 hour after feeding. These results may indicate that the concentrations of free lysine in plasma and PPC, under the condition of devoided lysine in diet, were more quickly droped than the reduction of feed intake rate. Hence, it is expected that PPC in brain might be a part of response area for limited amino acid.

• Journal of Chest Surgery
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• v.38 no.4 s.249
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• pp.301-307
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• 2005

Primary cardiac tumors are known to be rare. We studied the surgical results for primary cardiac tumors. Material and Method: Between August 1980 and December 2003, we classified 86 patients who had operation for primary cardiac tumors in our center into 3 groups; myxoma, nonmyxoma benign tumors, and malignant tumors. The mean age was $44.3\pm20.8$ years and 59 patients $(66.3\%)$ were female. In postoperative pathologic diagnosis, there were 81 cases $(94.2\%)$ of benign tumors in which myxoma was the most common tumor $(70\;cases,\;78.7\%);$ 5 fibroma $(5.6\%)$, 3 rhabdomyoma $(3.4\%)$, and 5 malignant tumors $(5.8\%)$. Result: $86.4\%$ of benign tumor was myxoma and the mean age was $50.4\pm15.4\;(range\;7\~80)$ years. Tumor was more common in females (49 cases) and most common preoperative symptom was dyspnea $(62.9\%)$. 57 cases were located at left atrial septum and only one case, which was located at right ventricular septum, was resected incompletely. There were no hospital deaths and one patient had mitral valve replacement on the first operative day due to newly developed postoperative mitral regurgitation. The mean follow up period was $109.3\pm71.8$ months and there was no evidence of recurrence in this period. 11 cases $(12.8\%)$ were non myxoma benign tumors; 5 fibromas, 3 rhabdo-myomas, etc. There were two hospital deaths and the causes of death were fungal endocarditis and hypoxia. There were no reoperations in nonmyxoma benign tumors. Malignant tumors were in 5 cases $(5.8\%);$ undifferentiated sarcoma in 2, rhabdomyosarcoma in 1, etc. Although there were no hospital mortalities, 3 patients who were followed up died from complications of tumors. Conclusion: Myxomas showed very excellent prognosis after complete resection and nonmyxoma benign tumors showed relatively good results for relief of symptoms. Surgery helped to relieve symptoms for malignant tumors, but the prognosis was poor.

• Journal of Chest Surgery
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• v.34 no.11
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• pp.848-853
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• 2001

Background: Sternal infection or dehiscence after cardiac surgery through median sternotomy is rare. If suitable treatment is not performed for the complication, however, the mortality is high. For 12 patients with sternal dehiscence or infection, we performed wide excision of the infected and necrotic tissue and covered with muscle flap(s) to obliterate the mediastinal dead space. Material and method: Sternal infection or dehiscence occurred in 13 of patients who underwent cardiac surgery One patient, who died of cerebral infarction before the sternal complication was treated, was excluded in this study. The sternal wound complication occurred in 6 of patients with valve replacement and 6 of patients with coronary bypass surgery, respectively. Since 1991, 9 patients underwent definite surgical debridement and muscle transposition as soon as fever was controlled with closed irrigation and drainage. The necrotic tissue and bone was widely excised and the sternal dead space was eradicated with the single flap or the combined flaps of right pectoralis flap(turnover flap), left pectoralis flap(turnover flap or rotation-advancement flap), and right rectus muscle flap. Result : There was no mortality in 12 patients with coverage of muscle flap(s) for sternal infection or dehiscence The mean interval between the diagnosis of sternal complication and the myoplasty was 6.6$\pm$3.9 days. In 4 patients, one pectoralis muscle flap was used, and in 8 patients both pectoralis muscle flaps were used. For each 1 patient and 2 patients in each group, right rectus muscle flap was added. For the last 3 patients, a single pectoralis flap was used to eradicate the mediastinal dead space and the longer placement of the mediastinal drain catheter was needed. One patient, who had suffered from necrosis of left pectoralis flap(rotation-advancement flap) with subsequent chest wall abscess after coverage of both pectoralis flaps, was managed with reoperation using right rectum flap. Conclusion : Sternal dehiscence or infection after cardiac operation can be readily managed with wide excision of necrotic infected tissue(including bone) and muscle flap coverage after short-term irrigation of sternal wound. The sternal(mediastinal) dead space may be completely eradicated with right pectoralis major muscle flap alone.

• Journal of Chest Surgery
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• v.36 no.3
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• pp.142-149
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• 2003

To know the feasibility of the coronary artery bypass graft (CABG) for multivessel coronary artery disease with purely bilateral internal thoracic arteries (ITAs), we analyzed the short-term clinical results and the coronary angiography of the patients. Material and Method: From March 2001 to June 2002, four hundred and five patients underwent CABG. Purely bilateral ITAs were used in 159 patients (39.3%). We analyzed these patients retrospectively The mean age of these patients was $61.2{\pm}8.5$ (range: 30 ~80) years and there were 123 male patients. The preoperative risk factors were as follows: diabetes in 54 patients (34.0%), history of acute myocardiac infarction within 4 weeks in 29 (18.2%), and emergency operation in 6 (3.8%). Off-pump CABG was carried out in 128 patients (80.5%). Associated procedures were mitral valvuloplasty (5), aortic valve replacement (3), Dor procedure (1), and so on. Result: The mean number of distal anastomoses was $3.1{\pm}0.9$ (range: 2~6), the mean duration of hospital stay was $8.4{\pm}4.5$ days. There was one (0.6%) operative death. Except for one early death, no other patients suffered from low cardiac output. The other postoperative complications were occurred as follows: reoperation due to bleeding in 3 patients, perioperative myocardiac infarction in 1, transient cardiac arrest in 2, transient cognitive dysfunction in 7, and transient ischemic attack in 1, and deep sternal wound infection in 1 patient. Recently, early postoperative angiography was performed in 19 patients who had triple vessel disease. The total number of distal anastomosis was 78 (mean $4.1{\pm}0.8$/patient). All distal anastomosis sites were patent, but competition flow was observed at the bypass sites where the native coronary artery stenosis was not significant. Conclusion: The CABG with purely bilateral ITAs for triple vessel disease was performed safely. The early patency rate was relatively good in small number of patients. However the long-term patency rate and the functional study to evaluate the sites where competition flow was observed should be followed.

• Journal of Chest Surgery
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• v.37 no.9
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• pp.768-773
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• 2004

Failure of mitral valve repair sometimes may be ascribed to severe or progressive alteration of the subvalvar apparatus. The aim of this study was to evaluate the effects of new chordae formation on mitral repair. Material and Method: From March 1997 to february 1999, 26 patients underwent mitral valve repairs with new chordae formation, we compared the symptoms and echocardiographic findings checked at preoperative state, and intraoperative period, discharge, and their last OPD visit. There were 45 male, and 11 female patients, and their mean age was 51.2$\pm$43.4 years. Etiology of the lesions was degenerative (18), rheumatic (6), infective (1) and ischemic (1). Chordal lesions were caused by rupture (18), elongation (6), and a combination of two causes (2). Associated lesions included atrial septal defect (2), tricuspid insufficiency (7), aortic insufficiency(4), and a combination of previous two factors (2). The number of mean artificial chordae was 3.6$\pm$1.6. Annuloplasty was per-formed in all cases. The CPB time was 182,1$\pm$63.7 minutes and the ACC time was 133.1$\pm$45.6 minutes. Aver-age follow up period was 49.2$\pm$7.1 months. Result: There was no early death. Early reoperation was performed in bud patients, one patient received mitral valve replacement because of an abnormality of annuloplasty and ano-ther received pericardiostomy due to postoperative pericardial effusion. During the follow up of 49.2$\pm$7.1 moths, there was no late mortality. Postoperative NYHA functional class checked at last OPD visit was class I in 22 patients (88%), class II in 2 (8%), and class III in 1 (4%). Regarding the late echocardiogram MR was absent in 20 patients (78%), 1 in 4 (15%), and II in 1 (4%). The postrepair mitral valve area was 2.2$\pm$0.35 $\textrm{cm}^2$ Conclusion: This study suggests that mitral valve repair using new chordae formation provides good early and mid term survivals and functional improvement. We think that the artificial chorda formation with polytetrafluoroethylene suture might be safe and effective technique for mitral valve repair.

• Journal of Chest Surgery
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• v.36 no.12
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• pp.921-927
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• 2003

Arterial switch operation (ASO) has been the most effective surgical option for transposition of the great arteries. But, the inappropriate dilation of the neoaortic root has been reported and its effect on neoaortic valve function and growth of aorta has not been well documented. Material and Method: Forty-eight patients who underwent cardiac catheterization during follow up after arterial switch operation were included in this study. Arterial switch operation was performed at a median age of 18 days (range 1∼211 days). Preoperative cardiac catheterization was performed in 26 patients and postoperative catheterization was performed in all patients at 15.8$\pm$9.6 months after ASO. Postoperative ratios of the diameters of neoaortic annulus, root and aortic anastomosis against the descending aorta were compared to the size of preoperative pulmonary annular, root and sinotubular junction. Preoperative and operative parameters were analyzed for the risk factors of neoaortic insufficiency. Result: There were two clinically significant neoaortic insufficiencies (grade$\geq$II/IV) during follow up, one of which required aortic valve replacement. Another patient required reoperation due to aortic stenosis on the anastomosis site. Post-operatively, neoaortic annulus/DA ratio increased from 1.33$\pm$0.28 to 1.52$\pm$.033 (p=0.01) and neoaortic root/DA ratio increased form 2.02$\pm$0.40 to 2.56$\pm$0.38 (p<0.0001). However, the aortic anastomosis/DA ratio showed no statistically significant difference (p=0.06). There was no statistically significant correlation between the occurrence of neoaortic insufficiency and neoaortic annulus/DA ratio and neoaortic root/DA ratio. Non-neonatal repair (age>30days) (p=0.02), preopeative native pulmonaic valve stenosis (p=0.01), and bisuspid pulmonic valve (p=0.03) were the risk factors for neoaortic insufficiency in univariate risk factor analysis. Conclusion: After ASO, aortic anastomosis site showed normal growth pattern proportional to the descending aorta, but neoaortic valve annulus and root were disproportionally dilated. Significant neoaortic valve insufficiency rarely developed after ASO and neoaortic annulus and root size do not correlate with the presence of postoperative neoarotic insufficiency. ASO after neonatal period, preoperative native pulmonary valve stenosis, and bicuspid native pulmonic valve are risk factors for the development of neoaortic insufficiency.

• Journal of Chest Surgery
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• v.36 no.3
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• pp.136-141
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• 2003

We assessed the intermediate-term result of tricuspid annuloplasty (TAP) for tricuspid valve regurgitation (TR) associated with congenital heart disease in adults. Risk factors for residual TR were also analysed. Material and Method: From August 1989 to June 2001, seventy three adult patients, 51 females and 22 males, underwent TAP for TR associated with various congenital heart disease. Their age ranged from 46 years to 73 years (mean:43). Associated heart anomalies were atrial septal defect (55), ventricular septal defect (6), partial anomalous pulmonary venous return (4) and others (8). Preoperative and post-operative TR velocities were 3.25 m/sec and 2.56 m/sec respectively, and the types of TAP were De Vega in 43, Kay in 18 and Ring annuloplasty in 12. Postoperative follow-up duration was 2,347 patient-month (mean: 32.6 months), and 134 two-dimensional echocardiographic examinations were done during this period. Residual TR greater than III/IV was considered as TAP failure. Result: TAP failure was observed in 7 patients (9.6%), and one patient among them underwent tricuspid valve replacement. Risk factors for TAP failure were diagnosis other than atrial septal defect (p=0.001), preoperative (p=0.038) and postoperative (p=0.028) high TR velocity. There was no statistical significance in terms of TAP methods. Conclusion: Careful evaluation of valve morphology and aggressive surgical intervention are mandatory for the repair of TR with preoperative or residual RV pressure overload.