Overcoming the Diffraction Limit Using Multiple Light Scattering in a Highly Disordered Medium

Choi, Youngwoon,Yang, Taeseok Daniel,Fang-Yen, Christopher,Kang, Pilsung,Lee, Kyoung Jin,Dasari, Ramachandra R.,Feld, Michael S.,Choi, Wonshik American Physical Society 2011 Physical review letters Vol.107 No.2

Immediate Effects of Posteroanterior Cervical Mobilization on Pressure Pain Threshold and Gait Parameters in Patients with Chronic Neck Pain: A Pilot Study

Taeseok Choi,Okkon Moon,Wansuk Choi,Seoyoon Heo,Sangbin Lee 국제물리치료연구학회 2019 Journal of International Academy of Physical Ther Vol.10 No.4

Background: Mobilization and cranio-cervical flexion exercise has been reported in reducing pain from cervical part and improving its motor function; also, has been represented that alleviate of neck pain and recover of neck muscles improve the normal gait performance. However, few studies have identified the effects of mobilization and exercise on pain and gait parameters with preceding issues. Objective: To examine the effects or changes of pressure pain threshold (PPT) and gait parameters in patients with chronic neck pain. Design: Cross-Sectional Clinical Trials Methods: Twenty patients with the history of neck pain (>3 months) performed the cervical mobilization and cranio-cervical flexion exercise. Gait parameters were assessed with wireless device and collected data were transmitted to the personal computer via Bluetooth. The PPT was measured posteroanterior direction at the prone position and the mean of subsequent three PPT measurements was used for the final analysis. Results: Both cervical central posteroanterior mobilization (CCPAM) (p<.000) and sling-based cranio-cervical flexion exercise (SBCCFE) (p<.000) group showed a significant increase in the PPT and the gait parameters, cadence (p<.023), was significantly increased in the CCPAM group, however slightly increased in the SBCCFE group. The comparison between the CCPAM and the SBCCFE groups after treatment did not show significant differences for the score on the PPT and gait parameters. Conclusions: This study suggests that CCPAM and SBCCFE increase PPT, cadence, and gait speed.

항공사진을 이용한 정밀도로지도 구축 가능성 분석

최태석(Taeseok Choi),최윤수(Yunsoo Choi),우병진(Byeongjin Woo),장수영(Sooyoung Chang) 대한공간정보학회 2020 한국지형공간정보학회 학술대회 Vol.2020 No.6

지상 LiDAR를 이용한 하수사각형거 안전점검 개선방안에 대한 연구

최태석(Taeseok Choi),양석철(Seokcheol Yang),최윤수(Yunsoo Choi),윤하수(Hasu Yoon) 대한공간정보학회 2020 한국공간정보학회 학술대회 Vol.2020 No.11

Effects of Lumbar Mobilization for Lower Limb Strength in Healthy Individuals: A Protocol for Systematic Review and Meta-Analysis

Wansuk Choi,Taeseok Choi,Hojung An,Jisung Kim,Seoyoon Heo 국제물리치료연구학회 2020 Journal of International Academy of Physical Ther Vol.11 No.2

Background: The effect of mobilization on lumbar back pain has been fully described in several clinical aspects, but evidence for muscle strength would be still less clear. Objective: To assess the effect of lumbar mobilization on lower limb strength in healthy individuals. Methods and Analysis: Healthy people aged 18-65 will be included regardless of race or sex. Original peer-reviewed primary reporting randomized controlled trials (RCTs) will be included. Electronic databases, such as MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Web of Science, Pedro, CINAHL, ClinicalTrials.gov will be searched from inception until July 30. Only studies published in English will be included in this review. Two reviewers will complete the screening for eligibility independently, and the other two reviewers will also complete the risks of data extraction and bias assessment independently. Lower Limb strength will be assessed as primary outcome, and particular intervention or participant characteristics will be assessed as the secondary outcomes. Meta-analysis will be conducted using Review Manager 5.3.3, and evidence level will be assessed using the method for Grading of Recommendations Assessment, Development and Evaluation. Outcomes will be presented as the weighted mean difference or standardized mean difference with 95% CI. If I2 ≤ 50%, P>.1, the fixed effect model will be used, otherwise, random-effects model will be used. Ethics and dissemination: This review might not be necessary ethical approval because it does not require individual patient’s data; these findings will be published in conference presentations or peer-reviewed journal articles. PROSPERO registration number: CRD42020150144.

Laboratory Experiments for the Force and Load with Pseudo-Dynamic Test: Ex-vivo Study for the Manual Therapy

Wansuk Choi,Taeseok Choi,Seoyoon Heo,Wooram Lee 국제물리치료연구학회 2019 Journal of International Academy of Physical Ther Vol.10 No.4

Background: Because of the lack of accurate values for applied forces in manual therapy, manual therapists relies on the magnitude of the individual’s perception during applying the force. However, excessive loading maneuvers carry risks for patients. Objective: To establish the relationship between the maximal force applied to swine skin with the specific region, sex, and baseline parameters of the subject. Design: Ex-vivo Study and laboratory Experimental research Methods: 3.5 kg of Korean pork sirloin that is a piece of swine was handled and it was set 3 dimensions; #A; #B; #C. Forty-seven participants who has no experience in physical therapy randomly carried out the experiment, indicated to push each place of the pressure spots with same posture and process under supervision from the instructor who has over 15 years of manual therapy, and we measured the pressure force in each time. Results: The biggest pressure force was recorded in spot #A, and #B was represented after #C. Pressure on #A showed certain statistic relation with height (r=.317, p<.05) and weight (r=.434, p<.01); pressure on #B showed certain relation which has statistical meaning with only height (r=.401, p<.01); pressure on #C emerged to have statistic relationship with height (r=.308, p< .05)and weight (r=.428, p<.01). The age aspect revealed relation with pressure on #A, #B and #C, but that was not statistically significant. Conclusions: It can be inferred that there is the most loss of pressure in the area where cartilage is like an island in the middle.

고도보정 노즐의 기술 및 특허 동향

최준섭(Junsub Choi),문태석(Taeseok Moon),최종인(Jongin Choi),박상현(Sanghyeon Park),김한솔(Hansol Kim),허환일(Hwanil Huh) 한국항공우주학회 2018 韓國航空宇宙學會誌 Vol.46 No.8

고도보정 노즐은 모든 고도에서 최적의 성능을 발휘할 수 있도록 고안된 노즐이다. 발사체의 비추력을 향상시키기 위한 방법으로는 연소실만의 특성인 특성배기속도를 향상시키는 방법과 노즐만의 특성인 추력계수를 향상시키는 방법이 있다. 고도보정 노즐은 동일한 연소기에서 노즐의 성능 개선을 통해 발사체의 성능향상을 가능하게 한다. 고도보정 노즐에 대한 연구는 독일 DLR에서 활발하게 진행되고 있으며, 미국, 러시아, 영국, 호주, 일본 등 항공우주선진국에서도 진행되고 있다. 본 논문에서는 고도보정 노즐에 대한 기술 현황 및 특허 동향에 대해 조사하였다. 이를 바탕으로 고도보정 노즐의 기술흐름을 파악하고 발사체 성능향상 연구에 기초자료로 활용하고자 한다. The altitude compensation nozzle is a nozzle designed for optimum performance at all altitudes. A method of improving the specific impulse of the space launch vehicle is a method of improving the characteristic exhaust velocity which is a characteristic of the combustion chamber and a method of improving the thrust coefficient which is a characteristic of the nozzle. The altitude compensation nozzle enables improvement of the performance of the space launch vehicle by improving the nozzle performance for the same combustor. Research on altitude compensation nozzles has been actively carried out in the DLR in Germany and is being carried out in advanced countries such as the US, Russia, UK, Australia and Japan. In this paper, the technology trends and patent trends of altitude compensation nozzles are investigated and summarized. Based on this, the technical trends of altitude compensation nozzles is grasped and utilized as basic data for the study on the performance improvement of a launch vehicle.

Immediate Effect of Spinal Mobilization on Lower Limb Strength in Healthy Individuals: A Pilot Study

Hojung An,Junghyun Choi,Taeseok Choi,Seoyoon Heo,Chaegil Lim,Wansuk Choi 국제물리치료연구학회 2020 Journal of International Academy of Physical Ther Vol.11 No.2

Background: Spinal Mobilization is one of the manual therapy technique that clinicians have used to treat pain, however, there is still a lack of research on changes in strength in healthy people. Objectives: To investigate the effect of posterior-anterior lumbar mobilization on lower limb strength in healthy individuals. Design: Two-group pretest-posttest design. Methods: In this study, 23 healthy subjects aged 20 years were assigned to 12 lumbar mobilization group (LMG) and 12 sham group (SG) to perform intervention and measurement through pre- and post-design. Intervention was performed in LMG with grade III~IV on L3-5 of the lumbar spine, and lumbar mobilization was performed for each segment. After intervention, knee flexion and extension strength were measured. To measure the main effect on muscle strength, a comparative analysis was conducted using paired t-test and independent t-test. Results: In LMG, knee flexor and extensor strength were increased significantly at 60°/s (P<.05). In addition, the extensors of LMG and SG were significantly different only at 60°/s, and the flexors were significantly different between groups at both 60°/s and 180°/s (P<.05). Conclusion: In healthy individuals, lumbar mobilization results in improvement of strength of knee flexor and extensor, and additional experiments on the effect of mobilization on the lumbar spine on functional changes in the lower limbs will be needed.

Effect of Molten Corium Behavior Uncertainty on the Severe Accident Progress

Choi, Wonjun,Kim, Taeseok,Jeon, Joongoo,Kim, Nam Kyung,Kim, Sung Joong Hindawi Limited 2018 Science and technology of nuclear installations Vol.2018 No.-

<P>Uncertainty of a severe accident code output needs to be handled reliably considering its use in safety regulation of nuclear industry. In particular, severe accident codes are utilized for probabilistic safety assessment (PSA), where the uncertainty of severe accident progress should be considered carefully due to its influence on human reliability analysis. Therefore, in this study, the uncertainty analysis of severe accident progress was performed using MELCOR code, and a total of 200 data sets of in-vessel uncertainty parameters were generated by Latin hypercube sampling method. The rank regression analysis was also performed to investigate the effect of uncertainty parameters on the severe accident progress. Sensitivity coefficients (SCs) in MELCOR such as molten clad drainage rate and zircaloy melt breakout temperature showed significant influence on relocation time and dryout time of lower plenum. However, the influence of uncertainty parameter diminished as the accident progressed.</P>

고도 보정용 확장-굴절(E-D) 노즐의 국외 연구 동향

문태석(Taeseok Moon),박상현(Sanghyeon Park),최준섭(Junsub Choi),허환일(Hwanil Huh) 한국항공우주학회 2017 韓國航空宇宙學會誌 Vol.45 No.10

E-D 노즐은 고도에 따라 노즐 내의 유효 면적을 변화시켜 고도 보정 효과를 통해 성능 이득을 가지는 노즐이다. E-D 노즐은 노즐의 길이를 절감시켜 발사체의 탑재중량이득을 얻을 수 있다고 알려져 있는데, 이러한 E-D 노즐의 장점과 잠재적인 가능성 때문에 영국, 독일, 호주, 유럽 등에서 관련된 연구가 수행되었다. 영국의 경우 E-D 노즐의 유동 특성과 고도 보정 노즐 중 듀얼 벨 노즐과의 성능 비교 연구를 수행하였고, DLR에서는 E-D 노즐의 천이 특성을 파악하기 위해 노즐 압력비 변화에 따른 천이 특성을 중점적으로 분석하였다. 유럽에서는 실제 발사체 Ariane 5 ESC-B 상단에 E-D 노즐 개념을 적용한 수치적 연구를 수행하여 노즐 길이 절감에 따른 탑재중량이득 가능성을 확인하였다. 본 논문에서는 국외에서 수행한 E-D 노즐의 연구 동향을 특징 별로 분류 및 분석하였고, 향후 E-D 노즐 연구의 기초 자료로 활용하고자 한다. The Expansion-Deflection(E-D) nozzle is a nozzle that has a performance gain through the altitude compensation effect by changing the effective area within the nozzle according to the altitude. An E-D nozzle has been known to reduce the length of the nozzle and achieve the payload gain of the launch vehicle. Due to the potential advantages of an E-D nozzle, related research has been carried out in the United Kingdom, Germany, Australia and Europe etc. In the UK, the flow characteristics of the E-D nozzle and the performance comparison with the dual-bell nozzle which is altitude compensation nozzle were studied. In order to understand the transition characteristics of the E-D nozzle in DLR, the transition characteristics according to the nozzle pressure ratio change were analyzed. In Europe, numerical study using the E-D nozzle concept on upper stage of the launch vehicle Ariane 5 ESC-B was carried out to confirm the possibility of payload gain according to the nozzle length reduction. In this paper, research trends of an E-D nozzle performed outside the country are classified and analyzed according to their characteristics and utilized as basic data of E-D nozzle research in the future.