• The Journal of Internal Korean Medicine
• /
• v.33 no.3
• /
• pp.257-271
• /
• 2012

Objectives : The purpose of this study was to confirm that the pulse analyzer is useful for analyzing characteristics of variables of pulse waves in age categories, evaluating pulse waves of the metabolic syndrome group, compared with those of the non-metabolic syndrome group in Korean adults. Methods : The pulse wave variables were measured in Guan of all 1,056 subjects by the pulse analyzer, using a pen-type piezoresistive sensor. The physical measurement, blood test and survey were also performed by each subject. Results : In the age categories, height of pre-incisura (h2), height of tidal wave (h3), area of percussion wave (Aw), and width of percussion wave (w) increased in accordance with increase in age. While ratio of systolic period area (As) went up according to the increase of age, ratio of diastolic period area (Ad) went down. Radial augmentation index (R-AI), h2/h1, h3/h1, w/t and angle of percussion wave went up by aging, generally. Aw rate (Aw/At) also increased. Among the metabolic syndrome group, in the ages of 19 and 44, ratio of systolic period area (As) was higher and ratio of diastolic period area (Ad) was lower than in the non-metabolic group. w/t, Aw/At, and angle of percussion wave were higher than in the non-metabolic syndrome group. Among the metabolic syndrome group over the age of 60, height of pre-incisura (h2), height of tidal wave (h3), total area (At), area of percussion wave (Aw), radial augmentation index (R-AI), h2/h1 and h3/h1 were higher than in the non-metabolic syndrome group. Conclusions : The pulse analyzer is useful to analyze arterial stiffness in the age categories and in the metabolic syndrome group by some measures.

• Proceedings of the KSR Conference
• /
• 2008.06a
• /
• pp.2114-2119
• /
• 2008

When a train enters into a tunnel, a compression wave is generated by a front nose and a expansion wave is generated by a rear nose each other. Because the compression wave and expansion wave have interactions with the train in a tunnel repeatedly, the internal pressure of the train is dramatically varied. And this pressure variation gives passengers discomfort like ear-ache. In this paper, we had measured the internal pressure variation of TTX developed and being on Test-Running in Honam line and made an analysis of pressure variation rate. As a result, the internal pressure variation was different as to the length of tunnel. Though the entering velocity of TTX is similar on test tunnels, on the short tunnel, the pressure drop was lower then that of the long tunnel. And it was expected that the rates of internal pressure variation would be exceeded the limits on 160km/h entering velocity.

• Journal of the Korean Society of Visualization
• /
• v.8 no.2
• /
• pp.31-39
• /
• 2010

Hysteresis is an effect by which the order of previous events influences the order of subsequent events. Hysteresis phenomenon of supersonic internal flows with shock waves has not yet been clarified satisfactorily. In the present study, experiments are carried out on internal flow in a supersonic nozzle to clarify the hysteresis phenomena for the shock waves. Flow visualization is carried out separately on the straight and divergent channels downstream of the nozzle throat section. Results obtained were compared with numerically simulated data. The results confirmed hysteresis phenomenon for shock wave in the Laval nozzle at a certain specific condition. The relationship between hysteresis phenomenon and the range of the rate of change of pressure ratio with time was shown experimentally. The existence of hysteretic behavior in the formation, both the location and strength, of shock wave in the straight part of the supersonic nozzle with a range of pressure ratio has also been confirmed numerically.

• Ocean Systems Engineering
• /
• v.6 no.1
• /
• pp.117-128
• /
• 2016

A theoretical study of Boussinesq equations (BEs) for internal waves propagating in a two-fluid system is presented in this paper. The two-fluid system is assumed to be bounded by two rigid plates. A set of three equations is firstly derived which has three main unknowns, the interfacial displacement and two velocity potentials at arbitrary elevations for upper and lower fluids, respectively. The determination of the optimal BEs requires a solution of depth parameters which can be uniquely solved by applying the $Pad{\acute{e}}$ approximation to dispersion relation. Some wave properties predicted by the optimal BEs are examined. The optimal model not only increases the applicable range of traditional BEs but also provides a novel aspect of internal wave studies.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.32 no.3
• /
• pp.267-273
• /
• 2008

The circular cylinder pipes are used in the many industrial areas. In this paper, the acoustic wave propagation in the pipe containing a gas is researched. First of all, the theory for the coupled acoustic wave propagation in a pipe is investigated. Acoustic wave propagation in pipe can not be occurred independently between the wave of the fluid and the shell. It requires complicated analysis. However, as a special case, the coupled wave in a high density pipe containing a light density medium is corresponded closely to the uncoupled in-vacuo shell waves and to the rigid-walled duct fluid waves. The coincidence frequencies of acoustic and shell modes contribute to the predominant energy transmission. The coincidence frequency means the frequency corresponding to the coincidence of the wavenumber in both acoustic and shell. In this paper, it is assumed that the internal medium is much lighter than the pipe shell. After the uncoupled acoustic wave in the internal medium and uncoupled shell wave are considered, the coincidence frequencies are found. The analysis is successfully confirmed by the verification of the experiment using the real long steel pipe. This work verifies that the coupled wave characteristic of the shell and the fluid is occurred as predominant energy transmission at the coincidence frequencies.

• Journal of Ocean Engineering and Technology
• /
• v.16 no.3
• /
• pp.34-39
• /
• 2002

본 논문에서는 수면파(Surface wave)와 수중파 (Internal wave)간의 동적 상관관계에 관하여 수행된 연구결과를 정리하였다. 표면파의 비선형 문제는 파의 경사매개변수를 2차원으로 가정하여 해석하였으며, Cauchy 문제는 불균일 조류상의 균일 수면중력파에 대하여 해석하였다. 또한, 파의 경사, 주기의 범위(Frequency range) 그리고 자유표면하의 조류의 분포들간의 조화에 대한 연구가 수행되었으며 해류 및 이동파와 연계되어 수중파의 최전 후방에 형성될 수 있는 정적 파형 (Steady wave pattern)이 수면파형에 포함되었다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.957-959
• /
• 2014

The wave analysis of cylinders combined rigidly with a finite plate to identify the effect of the plate on the wave propagation. This paper uses the mobility and impedance coupling method to combine a infinite-length cylinder with the plate, and obtains the coupling forces induced by the vibration of the structure. The waveguide finite element method is used to calculate the wave characteristics of the cylinder excited by the forces. From the results, the dispersion diagram can be obtained. It contains the characteristics induced by the vibration and length of the internal plate. It also shows the wave propagation of elastic waves sustained in the cylinder.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.21 no.2
• /
• pp.182-190
• /
• 2009

For RANS equation model using VOF scheme Lin and Liu (1999) developed internal wave-maker method to generate target wave trains by using designed mass source functions of the continuity equation. By using this method studies on various numerical wave experiments has been achieved without the problem caused by wave reflection due to an external wave-maker. In this study, the wave-maker method to generate target wave trains by using a momentum source function was proposed. The computational results obtained by applying the mass and momentum source functions into FLUENT were compared with each other. To see its applicability, the hydraulic experiment of Luth et al. (1994) were numerically simulated and their measurements are compared with the computations, and the vertical variations of computed results were shown and investigated.

• Kosin Medical Journal
• /
• v.33 no.3
• /
• pp.328-336
• /
• 2018

Objectives: Electrocardiograhy (ECG) is the first step in hypertrophic cardiomyopathy (HCMP) diagnosis. For various reasons, the T wave inversion (TWI) and ECG change with time and HCMP is not easy to diagnosis. The aim of this retrospective study was to investigate the association between TWI on ECG and apical HCMP. Methods: A total of 4,730 ECGs presenting TWI from January 2011 to March 2013 in Pusan National University Hospital were enrolled. 133 patients who were examined by both echocardiography and coronary angiogram were analyzed. Patients were divided into two groups: Group A (TWI ${\geq}$ 10 mm) and Group B (5 mm ${\leq}$ TWI < 10 mm). HCMP is defined by a wall thickness ${\geq}15mm$ in one or more LV myocardial segments. Apical HCMP is defined to be hypertrophy that is confined to LV apex. The patients who had ECGs with at least one month interval were divided 3 groups: Normal T wave, Abnormal T wave, and Persistent TWI. The prevalence of Apical HCMP and coronary artery disease (CAD) was reviewed among the three groups. Results: In this study there were a total 133 patients, with patients divided into Group A which had 15 patients and Group B which had 118 patients. Among the 23 patients with apical HCMP, three patients were Group A and twenty patients were Group B (P = 0.769). Regarding constancy of TWI, persistent TWI group was higher in apical HCMP than in other groups (P = 0.038). CAD had no difference between groups (P = 0.889). Conclusions: T wave negativity was not associated with incidence of apical HCMP. However, apical HCMP was diagnosed more frequently in patients with persistent TWI. Further follow up echocardiographic study is needed to evaluate the progression of apical HCMP in patients with TWI.

• The KSFM Journal of Fluid Machinery
• /
• v.11 no.3
• /
• pp.22-29
• /
• 2008

Clean and renewable energy technologies using ocean energy give us non-polluting alternatives to fossil and nuclear-fueled power plants to meet establishment of countermeasures against the global warming and growing demand for electrical energy. Among the ocean energy resources, wave power takes a growing interest because of its enormous amount of potential energy in the world. Therefore, various types of wave power conversion system to capture the energy of ocean waves have been developed. However, suitable turbine type is not normalized yet because of relatively low efficiency of the turbine systems. The purpose of this study is to investigate the internal flow and performance characteristics of a cross-flow type hydro turbine, which will be built in a caisson for wave power generation. Numerical simulation using a commercial CFD code is conducted to clarify the effects of the turbine rotation speed and flow rate variation on the turbine characteristics. The results show that the output power of the cross-flow type hydro turbine with symmetric nozzle shape is obtained mainly from Stage 2. Turbine inlet configuration should be designed to obtain large amount of flow rate because the static pressure and absolute tangential velocity are influenced considerably by inlet flow rate.