Earticle

In this study, a vibrating nozzle using the waste vibration energy of the compressor body was installed in the suction flow path to improve the efficiency of the compressor through the pre-compression. To this end, the behavior of the suction valve according to the vibrating nozzle and the mass flow rate of the refrigerant entering the compression chamber were numerically analyzed. The results showed that the mass flow rate increased proportionally as the angle of the vibration nozzle increased. Among the profile shapes of the vibration nozzle, the concave or straight shape showed the highest mass flow rate. Considering the ease of machining, the straight shape is more favorable. On the other hand, as the operating frequency and stroke of the vibration nozzle increased, the mass flow rate also increased proportionally. It can be seen that the largest nozzle angle, operating frequency, and stroke are favorable for pre-compression unless the suction flow is restricted.. In the future, it is necessary to apply the vibrating nozzle system to an actual compressor model to experimentally check the compressor's cooling power, compression work and EER.

The compressor of a refrigerator accounts for approximately 60-80% of the total energy consumption necessary for the refrigeration cycle. This study investigates the implementation of a pre-compression system featuring a vibrating nozzle, with the goal of enhancing the efficiency of a linear compressor. By utilizing this pre-compression system, the cooling capacity and efficiency of the compressor are expected to improve. The numerical results show that the pre-compression system leads to an improvement of approximately 1.7% in cooling capacity compared to the baseline model. Furthermore, an increase of approximately 0.1 in EER was observed, confirming the feasibility of incorporating a pre-compression system with a vibrating nozzle.

Purpose: The purpose of this study was to determine how the use of level D personal protective equipment (PPE) and cardiopulmonary resuscitation (CPR) feedback equipment affects chest compression (CC). Furthermore, this study provides basic data for developing Korean CPR guidelines that can be applied to patients with suspected or confirmed COVID-19. Methods: This randomized, single-blinded, crossover simulation trial included 26 student paramedics who performed 2-minute chest compressions using three different methods: Method A involved performing traditional CC for two minutes without donning level D PPE, Method B involved performing CC while donning level D PPE, and Method C involved performing CC with a CPR feedback device while donning level D PPE. Results: The use of a CPR feedback device during the 2-minute CC increased the exercise intensity of the subjects, but donning level D PPE didn't affect the quality of CC and the exercise intensity. The results of methods A and B showed changes in the quality of compression 80 seconds after the start of CC. No significant changes occurred in 2-minute CC when using the CPR feedback device. Conclusion: Using a CPR feedback device could prevent deterioration in the quality of CC while donning level D PPE.

PURPOSES : It is difficult to estimate tunnel stability because of lack of timely information during tunnel excavation. Tunnel deformability refers to the capacity of rock to strain under applied loads or unloads during tunnel excavation. This study was conducted to analyze a methods of pre-evaluation of stability during tunnel construction using the critical strain concept, which is applied to the results of tunnel settlement data and unconfined compression strength of intact rock or rock mass at the tunnel construction site. METHODS : Based on the critical strain concept, the pre-evaluation of stability of a tunnel was performed in the Daegu region, at a tunnel through andesite and granite rock. The critical strain concept is a method of predicting tunnel behavior from tunnel crown settlement data using the critical strain chart that is obtained from the relationship between strain and the unconfined compression strength of intact rock in a laboratory. RESULTS : In a pre-evaluation of stability of a tunnel, only actually measured crown settlement data is plotted on the lower position of the critical strain chart, to be compared with the total displacement of crown settlement, including precedent settlement and displacement data from before the settlement measurement. However, both cases show almost the same tunnel behavior. In an evaluation using rock mass instead of intact rock, the data for the rock mass strength is plotted on the lower portion of the critical strain chart, as a way to compare to the data for intact rock strength. CONCLUSIONS : From the results of the pre-evaluation of stability of the tunnel using the critical strain chart, we reaffirmed that it is possible to promptly evaluate the stability of a tunnel under construction. Moreover, this research shows that a safety evaluation using the actual instrumented crown settlement data with the unconfined compression strength of intact rock, rather than with the unconfined compression strength of a rock mass in the tunnel working face, is more conservative.

In case of a single input single output (SISO) system with a nonlinear term, a signal compression method is useful to identify a system because the equivalent impulse response of linear part from the system can be extracted by the method. However even though the signal compression method is useful to estimate uncertain parameters of the system, the method cannot be directly applied to a unique system with hysteresis characteristics because it cannot estimate all of the two different dynamic properties according to its motion direction. This paper proposes a signal compression method with a pre-processor to identify a unique system with two different dynamics according to its motion direction. The pre-processor plays a role of separating expansion and retraction properties from the system with hysteresis characteristics. For evaluating performance of the proposed approach, a simulation to estimate the assumed unknown parameters for an arbitrary known model is carried out. A motion platform with several single-rod cylinders is a representative unique system with two different dynamics, because each single-rod cylinder has expansion and retraction dynamic properties according to its motion direction. The nominal constant parameters of the motion platform are experimentally identified by using the proposed method. As its application, the identified parameters are applied to a design of a sliding mode controller for the simulator.

The purpose of this study was to find more effective method through comparison of manual chest compression and chest compression using $AutoPulse^{TM}$ device in pre-hospital simulation cardiac arrest. In order to achieve the purpose of the study, ambulance workers did two different style CPR in pre-hospital simulation cardiac arrest. Data analyzed by T test and ANOVA. Findings of this study are as follows. Firstly, manual chest compression is more effective than chest compression using $AutoPulse^{TM}$ device on scene. Secondly, chest compression using $AutoPulse^{TM}$ device is more effective manual chest compression in ambulance and in elevator. In conclusion, these findings provide strong evidence for the importance of hands off time and stable CPR before hospital arrival in explaining patient's prognosis. Therefore, strategies to conduct precise hands off time and stable CPR are needed to improve patient's prognosis.

In the design of the metal forming processes, various types of ductile fracture criteria are used to predict crack initiation and to fabricate metallic products without any defects. However, the quantitative measurement method for determination of crack initiation is insufficient. It is very difficult to detect crack initiation in ductile metals with excellent deformability because no significant load drop is observed due to crack generation. In this study, the applicability of acoustic emission sensors, which are commonly used in facility diagnostics, to measure crack initiation during the metal forming process was analyzed. Cylindrical notch specimens were designed using the finite element method to induce a premature crack on the surface of pre heat-treated steel (ESW90) material. In addition, specimens with various notch angles and heights were prepared and compression tests were carried out. During the compression tests, acoustic emission signal on the dies and images of the surface of the notch specimen were recorded using an optical camera in real time. The experimental results revealed that the acoustic emission sensor can be used to detect crack initiation in ductile metals due to severe plastic deformation.

배경: 새가슴의 수술적 치료는 완전한 늑연골의 절제와 흉골의 쐐기 골절술을 하는 변형된 라비치 술식을 주로 사용한다. 저자들은 수술을 간편하고 쉽게 하고자 변형된 튀어나온 늑연골만을 절제하고 흉골의 골절술없이 스테인레스 금속막대로 튀어나온 흉골을 앞에서 눌러 압박하는 방식으로 수술을 하였다. 이러한 방식으로 수술한 환자들을 대상으로 수술의 유용성과 효과 등을 평가하고자 본 연구를 시행하였다. 대상 및 방법: 2006년 7월부터 2008년 6월까지 새가슴으로 본원에서 부분 늑연골 절제와 스테인레스 금속막대를 이용한 흉골 압박 수술을 시행 받은 환자들 10명을 대상으로 진행을 하였다. 수술의 효과와 합병증 등을 관찰하였다. 결과: 새가슴만 단독으로 수술 받은 환자가 5명, 새가슴과 오목가슴이 같이 복합으로 존재하여 새가슴 수술과 오목가슴의 너스 수술을 같이 시행 받은 환자가 5명이었다. 환자들의 평균 연령은 13.4+3.3세였다. 평균 수술기간은 새가슴 단독 수술만 시행된 경우가 137.6+22.9분이었고 새가슴과 오목가슴이 공존하여 같이 수술을 받은 경우는 234.0+36.5분이었다. 평균 입원기간은 11.8+1.0일이었다. 새가슴의 술전 Halter's pectus index는 $2.10{\pm}0.21$에서 수술 후에는 $2.53{\pm}0.07$로 증가하였다. 합병증으로는 단순한 부분적인 창상균열이 1예 있었다. 결론: 저자들은 10명의 새가슴 환자들에게 변형된 튀어나온 늑연골만을 절제하고 흉골의 골절술 없이 스테인리스 금속막대로 튀어나온 흉골을 앞에서 눌러 압박하는 수술을 시행하여 좋은 결과를 얻었다. 이러한 저자들의 치료법은 기존의 라비치 수술법에 비하여 쉽고 간편한 수술법이다. 그러나 아직 금속막대의 제거가 모든 환자에서 완전히 이루어진 상태가 아니므로 정확한 치료효과에 관하여서는 좀 더 많은 수술례를 대상으로 장기적인 추적 관찰이 필요하다.

Background: The surgical treatment of pectus carinatum is usually a modified Ravitch operation that consists of complete costal cartilage resection and sternal wedge osteotomy. We tried a simple and easy technique that is resection of only deformed, protruded costal cartilage and pre-sternal compression with using a stainless steel bar and this is done without sternal osteotomy. Therefore, we performed partial cartilage resection and pre-sternal compression with a stainless steel bar and we observed the effects and the efficiency of treatment. Material and Method: From July, 2006 to June, 2008, 10 patients with pectus carinatum underwent our modified technique of pectus carinatum surgery. The effects of surgery and the complications were reviewed. Result: 5 patients with only pectus carinatum underwent our modified technique of pectus carinatum surgery. 5 patients with pectus carinatum and pectus excavatum underwent our modified technique of pectus carinatum surgery and Nuss surgery. The mean patient age was 13.4+3.3 years old. The mean operation time was 137.6+22.9 minutes for the pectus carinatum patients and 234.0+36.5 minutes for the pectus carinatum and pectus excavatum patients. The mean length of hospitalization was 11.8+1.0 days. The Haller pectus index of pectus carinatum was $2.10{\pm}0.21$ preoperatively and this was increased to $2.53{\pm}0.07$ postoperatively. The only complication was simple partial wound disruption in 1 patient. Conclusion: We performed partial cartilage resection and pre-sternal compression with a stainless steel bar in 10 patients with pectus carinatum and its effects were good. Our modified technique of pectus carinatum is easy and simple as compared with the Ravitch operation. But removal of the stainless steel bar has not yet been performed for these patients and long-term follow up is needed to accurately evaluate the. effects of this surgery in many surgical cases.

본 논문에서는 영상 데이터 압축을 위하여 2- 채널 멀티웨이브렛 변환을 적용하였다. 멀티웨이브렛 시스템은 음성 데이터 등의 비정상적인 신호의 압축에 스칼라 웨이브렛 시스템을 능가하는 우수한 성능을 나타내는 것으로 알려져 있으나 2차원 데이터인 영상 데이터의 경우에는 멀티웨이브렛 시스템 특유의 시각적 격자 오류가 발생하는 문제가 있다. 본문의 멀티웨이브렛 변환 및 압축 시스템에서는 멀티웨이브렛 효과에 의하여 발생하는 격자 오류를 제거하기 위하여 전후처리 필터링을 멀티웨이브렛 변환 및 압축 시스템에 접목하는 방법을 제시하였다. 또한, 제안한 시스템의 성능을 검증하기 위하여 컴퓨터 시뮬레이션을 수행하였으며 영상 데이터의 압축 기능 측면에서 스칼라 웨이브렛 시스템과 비교하였다. 이때, 비트 할당과 양자화를 위해서 전송율 결과는 제안한 멀티웨이브렛 변화 및 압축 시스템이 스칼라 웨이브렛 시스템 보다 영상 압축 성능 측면에서 1 ~ 2 dB 우수한 것으로 나타났다. 만약 SPIHT과 run-length 채널 부호화 기법 등의 우수한 압축 기술을 멀티웨이브렛 변환 시스템에 적용한다면 더욱 우수한 성능 개선 효과를 기대할 수 있을 것으로 사료된다.

Two-channel multiwavelet system is investigated for image compression application in this paper. Generally, multiwavelets are known for their superb capability of compressing non-stationary signals like voice. However, multivavelet system have a critical problem in processing and compressing image data due to mesh-grid visual artifacts. In our two-channel multiwavelet system we have investigated incorporation of pre and post filtering to the multiwavelet transform and compression system for alleviating those ingerent visual artifacts due to multiwavelet effect. In addition, to quantify the image data compression performance of proposed multiwavelet system, computer simulations have been performed using various image data. For bit allocation and quantization, the Lagrange multiplier technique considering data rate vs. distortion rate along with a nonlinear companding method are applied equallly to all systems considered, here. The simulation results have yielded 1 ~ 2 dB compression enhancement over the scalar savelet systems. If the more advanced compression methods like SPIHT and run-length channel coding were adopted for the proposed multiwavelet system, a much higher compression gain could be obtained.