• 한국기계가공학회지
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• 제21권1호
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• pp.95-101
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• 2022

This paper proposes a method to process the shape of an optical transmission road and attempts to determine the most suitable single processing method for an acrylic plate optical transmission road. In addition, by manufacturing an automatic pattern processing device to generate certain shapes on the acrylic plate at regular intervals, and measuring the illuminance of the patterned acrylic plate optical transmission road, the measured illuminance was confirmed to fall under the KS illuminance values presented in Table 1. In conclusion, when an incident light of approximately 20,000 lx is applied, the transmission illumination is approximately 200 lx, which represents a transmission rate of approximately 1% for incident light and corresponds to the KS illumination criterion F. Additionally, the right-angle triangular pyramid base size (A) processed at a temperature of 350 ℃ for one second was 2 mm, exhibiting the largest transmission illumination of 280 lx. When the transparent acrylic plate was set to a constant size of 1.6 mm at the bottom of the right-angle triangular pyramid, the fastest response occurred at a processing tip temperature of 350 ℃ (0.04 s). On the other hand, it took 10 s to process the size of the bottom of the right-angled triangular pyramid at a temperature of 200 ℃ to 1.6 mm, and it was confirmed that the optical transmission efficiency was significantly reduced because of the burr that occurred at this time.

• 한국컴퓨터정보학회논문지
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• 제28권2호
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• pp.39-46
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• 2023

본 논문은 클라이언트-서버 방식을 사용하는 대규모 1인칭 온라인 슈터 게임(MMOFPS)에서의 네트워크 부하를 줄이기 위한 효율적인 적응적 패킷전송 주기 방법을 제안한다. 플레이어 움직임에 있어서 빠르고 지속적인 변화와 정적이고 선형적인 상태가 다양하게 공존하는 FPS 게임의 특성상 변화의 정도에 따라 서버로의 패킷 전송량을 절약할 수 있는 지점들이 존재하는데, 이를 위해 본 논문에서는 클라이언트가 매 패킷을 전송할 때마다 플레이어의 위치 및 움직임 변수들의 변화량을 측정하여 이를 기반으로 다음번 패킷이 전송되어야 할 시간 간격을 계산한다. 서버 측에서는 받은 패킷의 정보들을 사용하여 다음 패킷이 도착할 때까지의 공백을 메우기 위해 위치 예측을 수행하여 모든 클라이언트에게 브로드캐스팅을 하게 된다. 긴 패킷 전송 간격으로 인한 예측 오차를 줄이기 위하여 전송 간격 최대한계치와 이중 패킷전송 등의 추가적 작업을 수행한다. 결과의 효율성을 보이기 위해 테스트 게임 환경을 구축하여 기존의 고정된 패킷전송 주기 시스템과의 비교분석을 수행하였다.

• 한국어병학회지
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• 제35권2호
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• pp.205-214
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• 2022

In recent years, there have been many studies investigating changes in animal behavior using video tracking technology to track motion. However, there have been very few studies and results on changes in the behavior of fish infected with a pathogen. Therefore, the present study attempted to analyze the behavior of angelfish (Pterophyllum scalare) infected with bacterial pathogens using video tracking. Two cameras were placed in front of the water tank to obtain behavior data, and tracking was performed for three days until the day of death. Data such as average speed, changes in speed, the locations of the fish in the tank, and fractal dimension were statistically analyzed based on the fish speed and location in the tank of the fish. For bacterial infection, an individual angelfish was intraperitoneally injected with approximately 10⁶ CFU ml^-1 of Aeromonas hydrophila or Edwardsiella piscicida. The experiment was carried out five times for each group. Fish infected with the bacterial pathogens showed a tendency to increase in speed and to spend more time in the upper part of the tank one or two days before death. On the day the fish died, the average speed, changes in speed, and the fractal dimension value were significantly lower than the corresponding values in the control group, and the fish also remained in the lower part of the tank. Our results indicated that behavioral changes in fish could be successfully detected earlier than death using video tracking technology, and that this method presents potential for disease monitoring in aquaculture.

• 한국전문물리치료학회지
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• 제29권1호
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• pp.54-63
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• 2022

Background: Low back and neck pain are two of the most common medical problems in the adult population. It is estimated that between 70% and 80% adults experience an episode of low back pain at least once during their lifetime. Objects: This study aimed to compare the effects of various stretching exercises and muscle energy techniques used for treatment of iliopsoas, quadratus lumborum, and hamstrings of patients with low back pain. Methods: A total of 52 subjects were randomly assigned to the control group (n = 17), the muscle energy technology group (METG, n = 19), and the stretching exercise group (SEG, n = 16). Interventions were performed twice a week for 4 weeks. Outcomes were measured before and after 4 weeks of treatment in the three groups, using the Korean version of the Oswestry Disability Index, the Visual Analogue Scale (VAS), the Fear Avoidance Belief Questionnaire (FABQ), the Finger to Floor test (FTF), the Modified-Modified Schober Test (MMS), and the Trunk Flexion Range of Motion test. Results: This study showed significant reduction in the pre-test and post-test KODI, VAS, and FABQ scores in all the three groups (p < 0.05). The KODI, VAS, FABQ and FTF assessed in this study showed interactions between the groups and the measurement time point (p < 0.01). After intervention, the KODI, VAS, FABQ and FTF in the SEG and METG were significantly higher (p < 0.05), and there was no difference between the METG and SEG. MMS and HFROM test showed no difference between the three groups (p > 0.05). Conclusion: KODI, VAS, FABQ and FTF showed significant improvement after basic physical therapy, muscle energy technique, and stretching exercise intervention. And there was no significant difference in the intervention effect between the muscle energy group and the stretching exercise group.

• Steel and Composite Structures
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• 제43권1호
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• pp.79-90
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• 2022

In this study, the dynamic behavior of functionally graded layered deep beams with viscoelastic core is investigated including the porosity effect. The material properties of functionally graded layers are assumed to vary continuously through thickness direction according to the power-law function. To investigate porosity effect in functionally graded layers, three different distribution models are considered. The viscoelastically cored deep beam is exposed to harmonic sinusoidal load. The composite beam is modeled based on plane stress assumption. The dynamic equations of motion of the composite beam are derived based on the Hamilton principle. Within the framework of the finite element method (FEM), 2D twelve -node plane element is exploited to discretize the space domain. The discretized finite element model is solved using the Newmark average acceleration technique. The validity of the developed procedure is demonstrated by comparing the obtained results and good agreement is detected. Parametric studies are conducted to demonstrate the applicability of the developed methodology to study and analyze the dynamic response of viscoelastically cored porous functionally graded deep beams. Effects of viscoelastic parameter, porosity parameter, graduation index on the dynamic behavior of porous functionally graded deep beams with viscoelastic core are investigated and discussed. Material damping and porosity have a significant effect on the forced vibration response under harmonic excitation force. Increasing the material viscosity parameters results in decreasing the vibrational amplitudes and increasing the vibration time period due to increasing damping effect. Obtained results are supportive for the design and manufacturing of such type of composite beam structures.

• Clinical Pain
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• 제19권1호
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• pp.1-7
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• 2020

Objective: A prospective, assessor-blinded, randomized controlled trial was conducted in patients with chronic low back pain to evaluate the efficacy of portable low power laser therapy (LPLT) and the effect when combined with exercise therapy on pain and functions. Method: 60 patients were recruited and 56 patients, excluding 4 dropouts, were randomly allocated to the LPLT group (Group 1: 19 patients), placebo laser therapy with exercise group (Group 2: 18 patients), and LPLT with exercise group (Group 3: 19 patients). Laser therapy and exercise was performed five times a week for 4 weeks. Visual analogue scale (VAS), Schober test, lumbar range of motion (ROM) measures (flexion, extension and lateral flexion), Oswestry Disability index (ODI) were measured at baseline, at 4 weeks after intervention, and at 6 weeks after 2 weeks of no intervention. Results: Statistically significant improvements were noted in all group by time interaction with respect to all outcome parameters (p<0.05). All parameters in each group improved not only in the period of treatment (4 weeks), but also in the final evaluation (6 weeks) 2 weeks after the end of treatment. Post-hoc analysis showed statistically significant difference between the LPLT with exercise group and the other groups in all outcome parameters except for the ODI at 4 weeks and at 6 weeks. Conclusion: Portable LPLT is effective treatment in reducing pain and improving lumbar ROM and with exercise is more effective than laser or exercise monotherapy for the chronic low back pain patients.

• Earthquakes and Structures
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• 제22권1호
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• pp.25-38
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• 2022

The RC private constructions represent a large part of the housing stock in the north part of Algeria. For various reasons, they are mostly built without any seismic considerations and their seismic vulnerability remains unknown for different levels of seismic intensity possible in the region. To support future seismic risk mitigation efforts in northern Algeria, this document assesses the seismic vulnerability of typical private RC constructions built after the Boumerdes earthquake (May 21, 2003) without considering existing seismic regulation, through the development of analytical fragility curves. The fragility curves are developed for four representative RC frames in terms of slight, moderate, extensive, and complete damage states suggested in HAZUS-MH 2.1, using nonlinear time history analyses. The numerical simulation of the nonlinear seismic response of the structures is performed using the SeismoStruct software. An original intensity measure (IM) is proposed and used in this study. It is the zone acceleration coefficient "A", through which the seismic hazard level is represented in the Algerian Seismic Regulations. The efficiency, practicality, and proficiency of the choice of IM are demonstrated. Incremental dynamic analyses are conducted under fifteen ground motion accelerograms compatible with the elastic target spectrum of the Algerian Seismic Regulations. In order to cover all the seismic zones of northern Algeria, the accelerograms are scaled from 0.1 to 2.5 in increments of 0.1. The results mainly indicate that private constructions built after the Boumerdes earthquake in the moderate and high seismic zones with four (04) or more storeys are highly vulnerable.

• 한국전산구조공학회논문집
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• 제35권1호
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• pp.1-8
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• 2022

본 연구에서는 토양-탄체 간 분리 및 재접촉을 고려한 IFL 기반 침투해석 기술을 개발하고 이를 기존 문헌의 실험결과와 비교하는 연구를 수행했다. 탄체를 강체로 가정한 후, 토양 내로 침투 시 발생하는 구형공동팽창 현상을 고려함으로써 탄체의 궤적을 예측할 수 있다. 토양에 대한 저항함수는 Mohr-Coulomb 항복 모델을 활용했으며, 입사각 혹은 AOA에 따른 J-hook 현상을 모사할 수 있다. 기존 문헌에서의 실험결과(총 6회)와의 비교 결과, 수치해석으로부터 예측한 탄체의 침투 깊이는 실험대비 약 13.4%의 평균오차를 나타냈다. 일반적으로 탄체의 침투 경로를 예측하기 위해 유한요소법이 널리 활용된다. 하지만, 유한요소법 활용 시, 탄체의 모델링을 위해 많은 시간과 노력이 필요하며, 해석 수행을 위해 수 시간이 소요된다. 본 연구를 통해 개발한 모델을 활용할 시, 탄체의 치수 입력만 필요하며 해석 시간도 수 초 이내이다.

• 한국해양공학회지
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• 제36권5호
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• pp.340-352
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• 2022

This article presents a modeling method for the uncorrelated measurement error of the ultra-short baseline (USBL) acoustic positioning system for aiding navigation of underwater vehicles. The Mahalanobis distance (MD) and principal component analysis are applied to decorrelate the errors of USBL measurements, which are correlated in the x- and y-directions and vary according to the relative direction and distance between a reference station and the underwater vehicles. The proposed method can decouple the radial-direction error and angular direction error from each USBL measurement, where the former and latter are independent and dependent, respectively, of the distance between the reference station and the vehicle. With the decorrelation of the USBL errors along the trajectory of the vehicles in every time step, the proposed method can reduce the threshold of the outlier decision level. To demonstrate the effectiveness of the proposed method, simulation studies were performed with motion data obtained from a field experiment involving an autonomous underwater vehicle and USBL signals generated numerically by matching the specifications of a specific USBL with the data of a global positioning system. The simulations indicated that the navigation system is more robust in rejecting outliers of the USBL measurements than conventional ones. In addition, it was shown that the erroneous estimation of the navigation system after a long USBL blackout can converge to the true states using the MD of the USBL measurements. The navigation systems using the uncorrelated error model of the USBL, therefore, can effectively eliminate USBL outliers without loss of uncontaminated signals.

• 한국지구과학회지
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• 제43권4호
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• pp.511-519
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• 2022

Given the significant social and economic impact caused by heat waves, there is a pressing need to predict them with high accuracy and reliability. In this study, we analyzed the real-time forecast data from six models constituting the Subseasonal-to-Seasonal (S2S) prediction project, to elucidate the key mechanisms contributing to the prediction of the recent record-breaking Korean heat wave event in 2018. Weekly anomalies were first obtained by subtracting the 2017-2020 mean values for both S2S model simulations and observations. By comparing four Korean heat-wave-related indices from S2S models to the observed data, we aimed to identify key climate processes affecting prediction accuracy. The results showed that superior performance at predicting the 2018 Korean heat wave was achieved when the model showed better prediction performance for the anomalous anticyclonic activity in the upper troposphere of Eastern Europe and the cyclonic circulation over the Western North Pacific (WNP) region compared to the observed data. Furthermore, the development of upper-tropospheric anticyclones in Eastern Europe was closely related to global warming and the occurrence of La Niña events. The anomalous cyclonic flow in the WNP region coincided with enhancements in Madden-Julian oscillation phases 4-6. Our results indicate that, for the accurate prediction of heat waves, such as the 2018 Korean heat wave, it is imperative for the S2S models to realistically reproduce the variabilities over the Eastern Europe and WNP regions.