• Journal of the Institute of Electronics Engineers of Korea TE
• /
• v.42 no.4
• /
• pp.27-32
• /
• 2005

Liquid valve is divided into cylinder and liquid part or composed of a single body structure. It becomes a connected structure to cylinder head after inserting stainless(STS) shaft to Teflon packing. In injecting and intercepting fluid, working efficiency becomes low because of the top and bottom round trip operation the friction between Teflon packing and STS shaft fluid leakage, decline of working environment, and each part replacement. And so target value is unattainable in productivity liquid valve design, quality, and structure change are studied. In this paper, designed to solve the existing problems basically, to prevent friction of Piston by developing diaphragm linked with piston, to satisfy long life, and to provide the prevention of leakage. The objective of the study is also to prevent remains fluid at nozzle tip after dispensing fluid, and bell close with the suction function in piston retreating.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.2
• /
• pp.139-146
• /
• 2021

In hybrid rocket combustion, the oxidizer swirl injection is frequently used to stabilize the combustion as the rotational velocity component affects the boundary layer flow. However, as the swirl strength increases, a problem arises where the combustion performance changes too much. Thus, this study attempts to control the low frequency instability while minimizing the change in combustion performance by adapting attenuated swirl injection with fuel insert used in reference [7]. To this end, a series of experimental tests were performed by varying swirl intensity and the location of the fuel insert. In the tests, the occurrence of combustion instability and combustion performance were closely monitored. The results confirmed that combustion instability was successfully suppressed at the condition of the swirl angle 6 degree and the location of fuel insert 310 mm. And, the changes in combustion pressure, O/F ratio, and fuel regression rate were found as minimal compared to the baseline case. Also the results reconfirmed that the formation of positive coupling between two high frequency oscillations in 500 Hz band, combustion pressure(p') and heat release oscillation(q'), is the necessary and sufficient condition of the occurrence of low frequency instability.

• The korean journal of orthodontics
• /
• v.28 no.5 s.70
• /
• pp.825-838
• /
• 1998

The purpose of this study was to evaluate the differences of soft tissue profile changes between the growing patients and the adult who had passed the growth peak, in orthodontic treatment with four premolar extractions. The results which was taken by correlating the soft tissue changes with hard tissue changes, lip thickness, molar relationship and arch length discrepancy in both groups was like the followings. 1. Significant hard tissue changes were decrease of VIs, VIi, UlPP, LlMP, HIi and increase of HPog'in adults and decrease of VIs, VIi and increase of VA, VPog'and all the vertical measurements in adolescents. 2. Significant soft tissue changes were decrease of VLs, VLi, and VILS in adults and increase of VSn, VSLS, VLs, VPog' and almost all vertical measurements in adolescents, and ${\Delta}LsE,\;{\Denta}LiE$ in adults and ${\Delta}LsE,\;{\Denta}LiE,\;{\Delta}LiSP\;and\;{\Delta}Mang$ was also significant 3. Correlation coefficient between ${\Delta}VIs\;and\;{\Delta}VLs$ was the greatest in adults and the next was ${\Delta}Ii/{\Delta}Li,\;{\Delta}Ii/{\Delta}ILS,\;{\Delta}ID/{\Delta}Li\;and\;{\Delta}ID/{\Delta}ILS$. In contrast all the vertical and horizontal measurements of hard and soft tissue in adolescents showed statistically significant corerrlation. 4. There were differences in correlation between soft tissue changes and incisor inclination and retraction at both groups, but the lower lip, nasolabial angle and mentolabial angle were commonly less influenced by the hard tissue changes in both groups. 5. The thinner the upper lip was, the more the ${\Delta}LsSP$ was in both groups, and the thinner the lower lip was, the more the ${\Delta}LiE\;and\;{\Denta}LiSP$ was in adolescents. 6. Molar relationship didn't influence the soft tissue profile changes. 7. Arch length discrepancy didn't influence the soft tissue profile changes.

• The korean journal of orthodontics
• /
• v.32 no.3 s.92
• /
• pp.195-207
• /
• 2002

Numerous studies have revealed the similarities and discrepancies in two divisions of class II malocclusion, since these malocclusion groups have been postulated to be disparate criterion, much as classified under one diagnostic umbrella. This study was undertaken to describe the craniofacial configurations of class II division 1 and 2, and consequently to discriminate the morphologic differences between the two malocclusion groups in Korean sample. Lateral headfilms of 34 class H division 1 and 29 division 2 were employed, while those of 142 adults of normal occlusion served as a control. The landmarks were digitized and 26 variables were statistically analyzed for one way ANOVA. 1. There manifested no statistically significant difference in maxillary position anteroposteriorly. Normal occlusion group exhibited most anteriorly positioned mandible, whereas class II division 1 showed the most retroposition. Class II division 1 disclosed clockwise rotation tendency of mandible, which resulted in position of the chin Posteriorly. 2. Class II division 1 showed greater in SN to MP, SN to PP significantly than other groups. 3. Class II division 2 showed smaller genial angle and larger mandibular body length than other groups. 4. Class II division 1 revealed greater anterior lower face height than other groups, whereas division 2 dictated significantly greater posterior face height. 5. Class II division 2 expressed the most retroclined lower incisor, while division 1 manifested the most proclination. The largest interincisal angle resided in Class II division 2 group. There were no significant differences in upper molar position anteroposteriorly.

• The korean journal of orthodontics
• /
• v.28 no.2 s.67
• /
• pp.189-201
• /
• 1998

The purpose of this study was to evaluate the characteristics of craniofacial skeleton on orthognathic surgical cases with skeletal Class III malocclusion. For this study, 74 students at the dental college of Chosun University volunteered as a normal occlusion group. They had well-balanced faces and good occlusions with acceptable Class I molar relationship. They had not received orthodontic treatment and had no signs or symptoms of temporomandibular joint dysfunction. 45 malocclusion patients enrolled for orthognathic surgical treatment with skeletal Class III malocclusion at the Department of Orthodontics, College of Dentistry, Chosun University. On the basis of this study. the results of this study were as follows: 1. Skeletal Class III malocclusion was largely due to the overgrowth of mandible in man and the undergrowth of maxilla in woman. 2. The mandible was antero-inferiorly overgrown by large MP-HP angle and large genial angle in orthognathic surgical cases with skeletal Class III malocclusion. And also, upper incisors were severely labioversioned, but on the other hand lower incisors were linguoversioned. 3. In female, lower-third facial height was characteristically shortened in comparison with middle-third facial height and also, lower facial throat angle was small in male.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.32 no.6
• /
• pp.446-457
• /
• 2020

Crescentic sand bar in the coastal zone of eastern Korea is a common morphological feature and the rhythmic patterns exist constantly except for high wave energy events. However, four consecutive typhoons that directly and indirectly affected the East Sea of Korea from September to October in 2019 impacted the formation of longshore uniform sand bar and overall shoreline retreats (approx. 2 m) although repetitive erosion and accretion patterns exist near the shoreline. Widely used XBeach to predict storm erosions in the beach is utilized to investigate the morphological response to a series of storms and each storm impact (NE-E wave incidence). Several calibration processes for improved XBeach modeling are conducted by recently reported calibration methods and the optimal calibration set obtained is applied to the numerical simulation. Using observed wave, tide, and pre & post-storm bathymetries data with optimal calibration set for XBeach input, XBeach successfully reproduces erosion and accretion patterns near MSL (BSS = 0.77 (Erosion profile), 0.87 (Accretion profile)) and observed the formation of the longshore uniform sandbar. As a result of analysis of simulated total sediment transport vectors and bed level changes at each storm peak Hs, the incident wave direction contributes considerable impact to the behavior of crescentic sandbar. Moreover, not only the wave height but also storm duration affects the magnitude of the sediment transport. However, model results suggest that additional calibration processes are needed to predict the exact crest position of bar and bed level changes across the inner surfzone.

• Economic and Environmental Geology
• /
• v.56 no.4
• /
• pp.435-445
• /
• 2023

A delta is a depositional landform that is formed when sediment transported by a river is deposited in a relatively low-energy environment, such as a lake, sea, or a main channel. Among these, a delta formed at the confluence of rivers has a great importance in river management and research because it has a significant impact on the hydraulic and sedimentological characteristics of the river. Recently, the equilibrium state of the confluence area has been disrupted by large-scale dredging and construction of levees in the Nakdong River. However, due to the natural recovery of the river, the confluence area is returning to its pre-dredging natural state through ongoing sedimentation. The time-series data show that the confluence delta has been steadily growing since the dredging, but once it reaches a certain size, it repeats growth and retreat, and the overall size does not change significantly. In this study, we developed a model to explain the sedimentation-erosion processes in the confluence area based on the assumption that the confluence delta reaches a dynamic equilibrium. The model is based on two fundamental principles: sedimentation due to supply from the tributary and erosion due to the main channel. The erosion coefficient that represents the Nakdong River confluence areas, was obtained using data from the tributaries of the Nakdong River. Sensitivity analyses were conducted using the developed model to understand how the confluence delta responds to changes in the sediment and water discharges of the tributary and the main channel, respectively. We then used annual average discharge of the Nakdong River's tributaries to predict the dynamic equilibrium positions of the confluence deltas. Finally, we conducted a simulation experiment on the development of the Gamcheon-Nakdong River delta using recorded daily discharge. The results showed that even though it is a simple model, it accurately predicted the dynamic equilibrium positions of the confluence deltas in the Nakdong River, including the areas where the delta had not formed, and those where the delta had already formed and predicted the trend of the response of the Gamcheon-Nakdong River delta. However, the actual retreat in the Gamcheon-Nakdong River delta was not captured fully due to errors and limitations in the simplification process. The insights through this study provide basic information on the sediment supply of the Nakdong River through the confluence areas, which can be implemented as a basic model for river maintenance and management.

• The korean journal of orthodontics
• /
• v.40 no.4
• /
• pp.227-238
• /
• 2010

Objective: The purpose of this study was to analyze the effect of growth hormone treatment (GHT) on craniofacial growth in children of short stature. Methods: Nineteen untreated children of short stature were referred from the Pediatric Department, Yeungnam University Hospital as a subject group. All subjects had lateral cephalograms taken before, after 1 year and after 2 years of growth hormone treatment. As a reference group, we selected 19 normal children with paired sampling who matched the subjects' age and sex, from the Department of Orthodontics, Kyungpook National University Hospital. Results: Before GHT, anterior cranial base length and upper posterior facial height, posterior total facial height, mandibular ramus length, and mandibular corpus length were significantly smaller in the reference group. In angular craniofacial measurements, saddle angle and mandibular plane angle were larger. SNA and SNB were smaller in the reference group. After two years of GHT, growth hormone accelerated growth in several craniofacial components. The posterior total facial height, the anterior, posterior cranial base length, and the mandibular ramus length were increased. And the difference in mandibular plane angle and ANB values compared with the reference group was decreased. Conclusions: GHT over 2 years leads to a craniofacial catch-up growth tendency, which is pronounced in interstitial cartilage and condylar cartilage.

• The Journal of Engineering Geology
• /
• v.27 no.4
• /
• pp.475-487
• /
• 2017

We performed landslide flume tests to analyze characteristics of landslide occurrence and change in the ground materials due to rainfall infiltration. The test apparatus is composed of flume, rainfall simulator, and measurement sensors and landslides were triggered by heavy rainfall (Intensity=200 mm/hr) sprinkled at the above of an artificial slope. The measurement sensors for matric suction and volumetric water content were installed with 3 sets at shallow (GL-0.2 m), middle (GL-0.4 m), and deep depth (GL-0.6 m) in the slope and the tests were performed with in-situ, loose, and dense condition of each weathered soils of granite, gneiss, and mudstone. The analyses show that surface erosion was dominant in initial time of the test due to heavy rainfall and then landslides occur following locally happened transverse tension cracks. The characteristics of landslide were both shallow failure because of a spread of wetting front induced by the rainfall infiltration and retrogressive failure. While the matric suction was decreased rapidly without any precursor in the soil saturation, the volumetric water content was increased gradually, reached its maximum value, and then decreased rapidly with landslide.

• The korean journal of orthodontics
• /
• v.39 no.2
• /
• pp.72-82
• /
• 2009

Objective: The purpose of this study was to investigate the structural changes of the hyoid bone and upper airway after orthognathic surgery for skeletal class III anterior open bite patients, and make comparisons with normal occlusion. Methods: Pre- and post-operative computed tomography (CT) examinations were performed on 12 skeletal class III anterior open bite patients who were treated with mandibular setback osteotomy. Using the V-works $4.0^{TM}$ program, 3-dimensional images of the total skull, mandible, hyoid bone, and upper airway were evaluated. Results: In the Class III open bite group, the hyoid bone were all positioned anteriorly, compared to the Normal group (p < 0.05). The angle between the hyoid plane and mandibular plane in the Class III openbite group before surgery was greater than in the Normal group (p < 0.05), and the difference increased after surgery (p < 0.01). In the Class III openbite group, the volume of the upper airway decreased after surgery (p < 0.001) and the volume of the upper airway was smaller than the Normal group before and after surgery (p < 0.001). Conclusions: The narrow upper airway space in skeletal Class III openbite patients decreased after mandibular setback osteotomy. This may affect the post-surgical stability.