• Fire Science and Engineering
• /
• v.29 no.1
• /
• pp.53-59
• /
• 2015

Water hammering created by an unsteady flow in pipeline systems can cause excessive change in pressure, vibration, and noise. So, water hammer analysis is very important for limiting the damage caused to pipeline, pump and valve systems by operation conditions. On the other hand, water hammer arrester has been manufactured and used in order to minimize the damage caused by water hammering phenomenon in domestic, and it has been produced and installed as the low cost-oriented because of being no separate standard in the meanwhile. Therefore, our research team investigated about the standardization of water hammer arrester performance through the various methods, such as test methods for verification of one pipe, assuming the occurrence of water hammer in a water-based fire extinguishing system, separated for opening impact pressure and shut off impact pressure and for a branch pipe in order to make guideline for water hammer arrester performance. And finally, verified the performance of the water hammer pressure as the simple mechanical way using the U-shaped pipe and a test weight, so KFI standards for the water hammer arrester could be established.

• Journal of Aerospace System Engineering
• /
• v.13 no.5
• /
• pp.72-78
• /
• 2019

Inlet hammershock is the critical loads condition for designing the inlet duct structure of a fighter. The sudden flow reduction in engine compressor causes inlet hammershock with high pressure. The traditional method was used to combine extreme conditions (maximum speed, sea level altitude, and cold day) to analyze this compression wave inlet hammershock pressure. However, after the 90s there have been papers that presented the probabilistic approach for the inlet hammershock to achieve the appropriate design pressure. This study shows how to analyze the inlet hammershock pressure by making practical use of the Republic of Korea Air Force real flight usage data under probabilistic approach and then analyze approximately 30% decreased inlet hammershock pressure compared with the traditional valve.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.14 no.1
• /
• pp.185-190
• /
• 2019

This study aims to apply the mathematical method of fractional order derivatives to the controller that controls the system response. In general, the Laplace transform of the PID controller has an exponent of the integer order of s. The derivative of the fractional order has a fractional exponent of s when it is transformed by Laplace transform. Therefore, this controller proposes a design method with the result of discrete time conversion. Because controllers with fractional exponents of s are not easy to design. This controller is applied to a standard secondary system and its performance is examined. Then, it applies to solenoid valve which is widely used in industrial field. A Luenberger's observer was designed to estimate the disturbance state and the observed state was applied to the fractional order controller. As a result, uniform and precise control performance was obtained. It was confirmed that the position error of the steady state is within 0.1 [%] and the rising time is within about 0.03 [s].

• Journal of Chest Surgery
• /
• v.55 no.5
• /
• pp.364-377
• /
• 2022

An anatomical understanding of the atrial myocardium is crucial for surgeons and interventionists who treat atrial arrhythmias. We reviewed the anatomy of the inter-nodal and intra-atrial conduction systems. The anterior inter-nodal route (#1) arises from the sinus node and runs through the ventral wall of the atrial chambers. The major branch of route #1 approaches the atrioventricular node from the anterior aspect. Other branches of route #1 are Bachmann's bundle and a vestibular branch around the tricuspid valve. The middle inter-nodal route (#2) begins with a broad span of fibers at the sinus venarum and extends to the superior limbus of the oval fossa. The major branch of route #2 joins with the branch of route #1 at the anterior part of the atrioventricular node. The posterior inter-nodal route (#3) is at the terminal crest and gives rise to many branches at the pectinate muscles of the right atrium and then approaches the posterior atrioventricular node after joining with the vestibular branch of route #1. The branches of the left part of Bachmann's bundle and the branches of the second inter-nodal route form a thin myocardial network at the posterior wall of the left atrium. These anatomical structures could be categorized into major routes and side branches. There are 9 or more anatomical circles in the atrial chambers that could be structural sites for macro re-entry. The implications of normal and abnormal structures of the myocardium for the pathogenesis and treatment of atrial arrhythmias are discussed.

• Journal of Chest Surgery
• /
• v.55 no.3
• /
• pp.233-238
• /
• 2022

Background: This study investigated the distribution of valve incompetence in patients with chronic venous disease (CVD) and its correlation with the clinical category of the clinical, etiological, anatomical, and pathophysiological (CEAP) classification. Methods: In total, 1,386 limbs with clinically suspected CVD were categorized according to the CEAP classification and consecutively underwent duplex ultrasonography between April 2017 and December 2020. Results: There were 362 limbs in male patients and 1,024 limbs in female patients. The limbs were classified as C0s-C1 (608 limbs, 43.8%), C2 (727 limbs, 52.5%), or C3-C6 (51 limbs, 3.7%). The prevalence of saphenous vein incompetence in CEAP C0s-C1 limbs was 43.6%. The saphenofemoral junction (SFJ) was competent in 37% of CEAP C2-C6 limbs. The CEAP C3-C6 category was not correlated with reflux patterns of the saphenous vein system (Cramer's V=0.07), incompetent SFJ (Cramer's V=0.07), deep vein reflux (Cramer's V=0.03), or the distribution of incompetent segments in the great saphenous vein (GSV) (Cramer's V=0.11). Conclusion: Duplex ultrasonography is necessary to formulate a proper treatment plan for limbs categorized as CEAP C0s-C1. The SFJ was competent in more than one-third of CEAP C2-C6 limbs with GSV reflux; as such, flush ligation of the GSV may be unnecessary in these patients. The CEAP C3-C6 category showed no correlations with reflux patterns of the saphenous vein system, SFJ reflux, deep vein reflux, or the distribution of incompetent segments in the GSV.

• Korean Circulation Journal
• /
• v.53 no.6
• /
• pp.406-417
• /
• 2023

Background and Objectives: Pathophysiological changes of right ventricle (RV) after repair of tetralogy of Fallot (TOF) are coupled with a highly compliant low-pressure pulmonary artery (PA) system. This study aimed to determine whether pulmonary vascular function was associated with RV parameters and exercise capacity, and its impact on RV remodeling after pulmonary valve replacement. Methods: In a total of 48 patients over 18 years of age with repaired TOF, pulmonary arterial elastance (Ea), RV volume data, and RV-PA coupling ratio were calculated and analyzed in relation to exercise capacity. Results: Patients with a low Ea showed a more severe pulmonary regurgitation volume index, greater RV end-diastolic volume index, and greater effective RV stroke volume (p=0.039, p=0.013, and p=0.011, respectively). Patients with a high Ea had lower exercise capacity than those with a low Ea (peak oxygen consumption [peak VO₂] rate: 25.8±7.7 vs. 34.3±5.5 mL/kg/min, respectively, p=0.003), while peak VO₂ was inversely correlated with Ea and mean PA pressure (p=0.004 and p=0.004, respectively). In the univariate analysis, a higher preoperative RV end-diastolic volume index and RV end-systolic volume index, left ventricular end-systolic volume index, and higher RV-PA coupling ratio were risk factors for suboptimal outcomes. Preoperative RV volume and RV-PA coupling ratio reflecting the adaptive PA system response are important factors in optimal postoperative results. Conclusions: We found that PA vascular dysfunction, presenting as elevated Ea in TOF, may contribute to exercise intolerance. However, Ea was inversely correlated with pulmonary regurgitation (PR) severity, which may prevent PR, RV dilatation, and left ventricular dilatation in the absence of significant pulmonary stenosis.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.41 no.7
• /
• pp.683-689
• /
• 2017

We have carried out the development for hydraulic breaker which can be operated by optimal mode with ICT convergence technology. This developed system can predict the rock properties. Moreover, this system can maximize the energy efficient with intelligent control of hydraulic system. In order to provide the optimal impact force, this system can measure the descending depth of piston with the proximity sensor and discriminate the rock properties with the measuring data and control the piston stroke using solenoid valve eventually. In addition, we have developed the controller, display module and operating device for cascade (multi-level impact) system and applied the module which can communicate each system by wireless communications. In conclusion, the control system which can control the multi-level impact in accordance with strength of rocks has been developed and approved by several field tests.

• Journal of Chest Surgery
• /
• v.55 no.5
• /
• pp.378-387
• /
• 2022

Background: Atrial fibrillation (Afib) is a marker of increased cardiovascular morbidity and mortality. Owing to the increased prevalence of Afib in patients undergoing cardiac surgery, assessing the effect of Afib on postsurgical outcomes is important. We aimed to analyze the effect of preoperative Afib on clinical outcomes in patients undergoing cardiac surgery using a large surgical database. Methods: This retrospective cohort study was based on the national health claims database established by the National Health Insurance Service of the Republic of Korea from 2009 to 2015. Diagnosis and procedure codes were used to identify diseases according to the International Statistical Classification of Diseases, 10th revision. Results: We included 1,037 patients (0.1%) who had undergone cardiac surgery from a randomized 1,000,000-patient cohort, and 15 patients (1.5%) treated with isolated surgical Afib ablation were excluded. Of these 1,022 patients, 412 (39.7%), 303 (29.2%), and 92 (9.0%) underwent coronary artery bypass, heart valve surgery, and Cox-maze surgery, respectively. Preoperative Afib was associated with higher patient mortality (p=0.028), regardless of the surgical procedure. Patients with preoperative Afib (n=190, 18.6%) experienced a higher cumulative risk of overall mortality (hazard ratio [HR], 1.435; 95% confidence interval [CI], 1.263-2.107; p=0.034). Subgroup analysis revealed a reduced risk of overall mortality with Cox-maze surgery in Afib patients (HR, 0.500; 95% CI, 0.266-0.938; p=0.031). Postoperative cerebral ischemia or hemorrhage events were not related to Afib. Conclusion: Preoperative Afib was independently associated with worse long-term postoperative outcomes after cardiac surgery. Concomitant Cox-maze surgery may improve the survival rate.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.22 no.2
• /
• pp.123-133
• /
• 2014

Minimizing the cylinder wear and the consumption rate of cylinder oil in a large two-stroke diesel engine is of great economic importance. A motor-driven cylinder lubricator for Sulzer RT-flex large two-stroke diesel engines developed by authors is in need of improving the lubricating system to lubricate cylinder parts optimally by an electronically controlled quill device according to changes of engine load and revolution speed. In order to apply the developed accumulating distributor to an integrated cylinder lubricator by the electronically controlled system as the third research stage, the lubricating system is improved in the electronically controlled quill device with a solenoid valve. In this study, the effects of lubricator revolution speed, driving pressure(or plunger stroke) and cylinder back pressure on oil feed rate and lubrication inequality rate are investigated by using the integrated cylinder lubricator system with an accumulated distribution by the electronic control(I.C.S.), and the oil feed rate and lubrication inequality rate of I.C.S. are compared with those of the motor-driven cylinder lubricator by the electronically controlled quill system equipped with an accumulating distributor(E.D.S.). It is found that the oil feed rate of I.C.S. is smaller than that of E.D.S. due to the reduction of delivery velocity by the higher delivery pressure, and the variances of lubrication inequality rate for I.C.S. have become smaller than those of E.D.S. as the driving pressure in all experimental conditions increases, except for the driving pressure of 26 bar(plunger stroke 2 mm) at the cylinder lubricator speed of 120 rpm.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.11
• /
• pp.688-694
• /
• 2018

The mixture ratio of two-component liquid silicone is important for the inherent physical characteristics of the finished product. Therefore, it is necessary to uniformly control the ratio of the main material and the sub-material. In this paper, a mixing-ratio control system was designed, which consists of a digital flow meter and a flow control system to measure the flow rate of the raw materials and a pumping system to maintain constant pressure and transfer of the raw materials. In addition, a program was developed to control the organic interlocking and mixing ratio. For the verification of the developed system, we compared the actual weight of raw material with the value measured by the flow meter during pumping, and we measured the physical properties of the mixed material by making test samples with and without the application of the mixing-ratio improvement algorithm. The measured value was close to the reference value with a hardness range of 46-47 and tensile strength of 9.3-9.5 MPa. These results show that the mixing ratio of the liquid silicone is controlled within an error range of ${\pm}0.5%$.