• 한국분무공학회지
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• 제24권2호
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• pp.66-72
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• 2019

Diesel vehicles suffer from poor starting and running problems at cold temperatures. Diesel vehicles have the characteristic that CO and PM are reduced or similarly discharged when going from low temperature to high temperature. In this study, a bypass type piezo injector for electronic control based common rail injection system was used. Numerical analysis using injector drive analysis model was performed to analyze injector drive and internal fuel flow characteristics according to fuel temperature change. The results show that the rate of density change due to the fuel temperature is proportional, and that the effect of the kinematic viscosity is relatively large between $-20^{\circ}C$ and $0^{\circ}C$. Comparing the results of temperature condition at $0^{\circ}C$ and $20^{\circ}C$, it is considered that the viscosity is more correlated with the needle displacement than the pressure chamber of the delivery chamber.

• 전력전자학회논문지
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• 제23권2호
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• pp.129-138
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• 2018

Previous single-phase transformerless inverters used active bypass switching circuits that need auxiliary power switches to minimize ground leakage current. However, switching and gate driving losses are increased due to the use of additional power switches. To cope with this drawback, this work proposes a transformerless inverter using a passive bypass filter without any auxiliary power switch. The operation and control of the proposed inverter are described. The ground leakage current characteristics are analyzed for the proposed inverter with the passive bypass filter. The experimental results of the proposed inverter for a 1.0kW prototype system are presented.

• 한국유체기계학회 논문집
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• 제10권6호
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• pp.17-23
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• 2007

In the present work, flow analysis has been performed in the steam turbine bypass control valve (single-path type) for two different cases i.e., case with steam only and case with both steam and water. The numerical analysis is performed by solving three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations. The shear stress transport (SST) model and $k-{\varepsilon}$ model are used to each different case as turbulence closure. Symmetry condition is applied at the mid plane of the valve while adiabatic condition is used at the outer wall of the cage. Grid independency test is performed to find the optimal number of grid points. The pressure and temperature distributions on the outer wall of the cage are analyzed. The mass flow rate at maximum plug opening condition is compared with the designed mass flow rate. The numerical analysis of multiphase mixing flow(liquid and vapor) is also performed to inspect liquid-vapor volume fraction of bypass valve. The result of volume fraction is useful to estimate both the safety and confidence of valve design.

• 한국환경보건학회지
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• 제23권4호
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• pp.57-66
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• 1997

Successful energy conservation and good indcfor air quality (IAQ) are highly dependent on ventilation system. Air filtration is a primary solution of indoor air control strategies in terms of reducing energy consumption and improving ihdoor air quality. A conventional system with bypass filter, as it is called variable-air-volume/bypass filtration system (VAV/BPFS), is a variation of the conventional variable air volume (VAV) systems, which is designed to eliminate indoor air pollutant and to save energy. Bypass filtration system equipped with a high-efficiency particulate filter and carbon absorbent provides additional cleaned air into indoor environments and maintain good IAQ for human health. The objectives of this research were to compare the relative total decay rate of indoor air pollutant concentrations, and to develop a mathematical model simulating the performance of VAV/BPFS. All experiments were performed in chamber under the controlled conditions. The specific conclusions of this research are: 1. The VAV/BPFS system is more efficient than the VAV system in removing indoor air pollutant concentration. The total decay rates of aerosol, and total volatile organic compound (TVOC) for the VAV/BPFS system were higher than those of the conventional VAV system. 2. IAQ model predictions of each pollutant agree closely with the measured values. 3. According to IAQ model evaluation, reduction of outdoor supply air results in decreased dilution removal rate and on increased bypass filtration removal rate with the VAV/BPFS. As a results, we recommends the VAV/BPFS as an alternative to conventional VAV systems.

• 동력기계공학회지
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• 제14권2호
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• pp.34-39
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• 2010

Recently, technical trend for machine tools is focused on enhancement of speed and accuracy. High speedy processing causes thermal and structural deformation of objects from the machine tools. Water cooler has to be applied to machine tools to reduce the thermal negative influence with accurate temperature controlling system. Existing On-Off control type can't control temperature accurately because compressor is operated and stopped repeatedly and causes increment of power consumption and decrement of the expected life of compressor. The goal of this study is to minimize temperature error in steady state. In addition, control period of an electronic expansion valve were considered to increment of lifetime of the machine tools and quality of product with a water cooler. PI controller is designed using type of hot-gas bypass for precise control of temperature. Gain of PI is decided easily by method of critical oscillation response, excellent performance of control is shown with 4.24% overshoot and ${\pm}0.2^{\circ}C$error of steady state. Also, error range of temperature is controlled within $0.2^{\circ}C$although disturbance occurs.

• 대한의생명과학회지
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• 제10권4호
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• pp.459-465
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• 2004

The use of hemofiltration has been proposed to reduce excessive body fluid and inflammatory mediators produced during cardiac surgery with cardiopulmonary bypass (CPB) in infants and children. This study was undertaken to evaluate the efficacy of hemofiltration in adult cardiac surgery using (CPB). Twenty adult patients scheduled for elective cardiac surgery were randomly assigned to control group without hemofiltration (n=10) or hemofilter group with hemofiltration during CPB (n=lO). CBC and serum levels of interleukin-6 (IL-6), D-dimer, endothelin-l (ET-1), and cortisol were measured at before the initiation and immediately after the termination of CPB (Pre-CPB and End-CPB, respectively). Clinical data were assessed at postoperative period. In hemofilter group hematocrit was significantly higher (30.04±2.63％ vs 23.30±2.71％, P=0.0014) whereas total leukocyte count was lower than in control group (7.71±1.78×10³/㎣ vs 16.01 ±3.12x10³/㎣, P=0.021) at End-CPB. Increased rate of IL-6 (311.56±97.31％ vs 825.45±102.56％, P=0.012) and D-dimer levels (154.55±89.04％ vs 308.33±157.64％, P=0.026) at End-CPB were significantly less in hemofilter group than in control group. Postoperative blood transfusion in hemofilter group was low compared with that of control group (741.00±38.07 ml vs 1,137.50±169.82 ml, P=0.037). There were no significant differences between two groups in platelet count, ET -1, cortisol, pulmonary index, mechanical ventilation, postoperative blood loss, ICU-stay and hospitalization. Hemofiltration technique applied in the present study provided partly beneficial effect in adult cardiac surgery.

• Asian-Australasian Journal of Animal Sciences
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• 제14권10호
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• pp.1405-1408
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• 2001

Ca salt of soybean oil (PSO) and that of mustard oil plus mahua oil (PMOMO) (50:50) were prepared using double decomposition method, and further tested for their fatty acid composition and degree of saponification. Furthermore, the different levels of protected fat of PSO and PMOMO were evaluated in wheat straw based total mixed ration (TMR) in vitro. Results indicated that capric, lauric, myristic, palmitic, steric, oleic, linoleic, leinolenic acids were traces, traces, traces, 10.00, 2.00, 25.00, 58.50, 5.0% in PSO while the corresponding values in PMOMO were 1.08, 0.28, 0.45, 16.9, 12.95, 44.38, 17.46 and 6.50%, respectively. The degree of saponification of both protected fat supplements was more than 80%. Six treatment combinations were tested I.e., blank without feed and fat supplement (T1); control diet with out fat supplement (T2); control diet plus bypass fat supplement (PSO) so that diet contain 5% fat (T3); control diet plus bypass fat supplement (PSO) so that diet contain 7.5% fat (T4); two more diets viz. T5 and T6 were formulated using bypass fat supplement from PMOMO containing 5 and 7.5% fat respectively. TMR was prepared using 50% concentrate mixture and 50% wheat straw. Result indicated that TVFA, $NH_3-N$,TCA-N, total-N and total gas production were increased in treatment diets at 7.5% level of supplementation, however, fermentation pattern remain similar at 5.0% level of supplementation with respect to control diet. Nevertheless, IVDMD and IVOMD values remained unchanged, rather non-significant at both fat levels and with the both fat sources. On the basis of results it was concluded that Ca-salt of Soybean oil or Mustard plus Mahua oil did not show any negative effect either on digestibility or on microbial protein synthesis in rumen, hence the dietary fat upto 7.5% level in total mixed ration based on wheat straw, could be safely used without any adverse effect on rumen fermentation.

• Journal of Chest Surgery
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• 제29권2호
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• pp.185-190
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• 1996

The effect of low-dose aprotinin on hemostasis in patients undergoing cardiopulmonary bypass (CPB) for repeat valve replacement and coronary artery bypass operations were investigated. Thirty patients undergoing elective CPB from February 1993 through February 1995 at Catholic Medical Center were studied. the patients were randomly divided into two groups(15 patients per group) : group 1, receive 1, 000, 000 KIU/kg aprotinin in the CPB priming volume and 20, 000 KIU/kg aprotinin intravenously each hour during CPB ; group 2, without aprotinin administration served as the controls. The result showed that the early postoperative (during the first 24 hours) and mean postoperative total blood loss of the aprotinin group were significantly reduced than the control group (317.2 $\pm$ 89.6ml in the aprotinin group versus 821.3 $\pm$ 441.2rnl in the control group, p<0.01 ; 767.2 $\pm$ 214.1 ml in the aprotinin group versus 1562.5 $\pm$ 735.2 rnl in the control gorup, p<0.01). Total use of packed red ells and fresh frozen plasma was higher in control group(1.22 $\pm$ 0.3 units versus 4.21 $\pm$ 1.7units of packed red cells, p<0.01 : and 2.37 $\pm$ 0.4units versus 6.72 $\pm$ 0.88uni1s of fresh prozen plasma, p<0.05). We conclude the low-dose aprotinin was positive influence on postoperative blood loss in undergoing highly bleeding potency cardiac operation.

• Journal of Chest Surgery
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• 제33권3호
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• pp.221-229
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• 2000

Background: Thromboxane A2 and endothelin-1 are the potent vasoconstrictors affecting pulmonary pathophysiology in response to whole body inflammatin following CPB. Aprotinin, as an antiiflammatory agent, may decrease the release of such vasoactive substance from pulmonary tissues, preventing pulmonary hypertension after cardiopulmonary bypass. Material and Method: Ten mongrel dogs(Bwt. ac. 20kg) were subjected to cardioupulmonary bypass for 2 hours and postbypass pulmonary vascular resistance(0, 1, 2, 3 hours) were compared with prebypass level. The dogs were divided into 2 groups; control group(n-5) and aprotinin group(n=5). In the aprotinin group, aprotinin was administered as follows; 50,000 KIU/kg mixed in pump priming solution, 50,000 KIU/kg prebypass intravenous infusion over 30 minutes, 10,000 KIU/kg/hour postbypass continuous infusion. Prebypass and postbypass 0, 1, 2, 3 hour pulmonary vascular resistance were measured. At prebypass and postbypass 0, 90, 180 minutes, blood samples were obtained from pulmonary arterial and left atrial catherers for the assay of plasma thromboxane B2 a stable metabolite of thromboxane A2, and endothelin-1 concentrations. Result: The ratios of pustbypass over prebypass pulmonary vascular at postbypass 0, 1, 2, 3 hours were 1.28$\pm$0.20, 1.82$\pm$0.23, 1.90$\pm$0.19, 2.14$\pm$0.18 in control group, 1.58$\pm$0.18, 1.73$\pm$0.01, 1.66$\pm$0.10, 1.50$\pm$0.08 in aprotinin group ; the ratios gradually increased in control group while decreased or fluctuated after postbypass 1 hour in aprotinin group. There was statistically significant difference between control group and aprotinin group at postbypass 3 hours(P=0.014). Pulmonary arterial plasma concentration of thromboxane B2(pg/ml) at prebypass, postbypass 0, 90, 180 minutes were 346.4$\pm$61.9, 529.3$\pm$197.6, 578.3$\pm$255.8, 493.3$\pm$171.3 in control group, 323.8$\pm$118.0, 422.6$\pm$75.6, 412.3$\pm$59.9, 394.5$\pm$154.0 in aprotinin group. Left atrial concentrations were 339.3$\pm$89.2, 667.0$\pm$65.7, 731.2$\pm$192.7, 607.5$\pm$165.9 in control group, 330.0$\pm$111.2, 468.4$\pm$190.3, 425.4$\pm$193.6, 4.7.3$\pm$142.8 in aprotinin group. These results showed decrement of pulmonary thromboxane A2 generation in aprotinin group. Pulmonary arterial concentrations of endothelin-1(fmol/ml) at the same time sequence were 7.84$\pm$0.31, 13.2$\pm$0.51, 15.0$\pm$1.22, 16.3$\pm$1.73 in control group, 7.76$\pm$0.12, 15.3$\pm$0.71, 22.6$\pm$6.62, 14.9$\pm$1.11 in aprotinin group. Left atrial concentrations were 7.61$\pm$17.2, 57.1$\pm$28.4, 18.9$\pm$18.2, 31.5$\pm$20.5 in control group, 5.61$\pm$7.61, 37.0$\pm$26.2, 28.6$\pm$21.7, 37.8$\pm$30.6 in aprotinin group. These results showed that aprotinin had no effect on plasma endothelin-1 concentration after cardiopulmonary bypass. Conclusion: Administration of aprotinin during cardiopulmonary bypass could attenuate the increase in pulmonary vascular resistance after bypass. Inhibition of pulmonary thromboxane A2 generation was thought to be one of the mechanism of this effect. Aprotinin had no effect on postbypass endothelin-1 concentration.

• Journal of Chest Surgery
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• 제23권2호
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• pp.268-274
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• 1990

Bleeding after cardiopulmonary bypass remains a cause for concern, requiring reexploration of the chest in approximately 3 percent of patients who have had operations on the heart. We examined the possibility that this problem might be alleviated by desmopressin acetate [DDAVP], synthetic vasopressin analogue that lacks vasoconstrictor activity. In a prospective, randomized trial, we studied the effect of intraoperative desmopressin acetate in 20 patients [the treated group 10 patients and the control group 10 patients] undergoing various cardiac operations requiring cardiopulmonary bypass. The result showed that the early postoperative [during first 24hrs] and mean postoperative blood loss [first 3 days] of the treated group were significantly reduced than the control group[447\ulcorner199ml in the treated group versus 746\ulcorner199ml in the treated group versus 746\ulcorner295 ml in the control group, p=0.014; mean\ulcornerstandard deviation and 675\ulcorner276 ml in the treated group versus 1006\ulcorner303 ml in control group, p=0.019]. The mean red-cell transfusion in first 3days were reduced in the treated group than the control group [3.3\ulcorner1.7 units vs 4.9\ulcorner1.7units, P=0.051]. There were no untoward side effects of desmopressin acetate. We conclude that the administration of desmopressin acetate can be recommended to reduce blood loss and blood conservation in patients undergoing cardiac operations.