• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.2
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• pp.131-134
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• 2011

We propose a spheroid chip that uses removable cell trapping barriers and that is capable of forming and extracting multicellular spheroids. By using a conventional well plate and flask, it is difficult to form small-sized spheroids, which resemble avascular 3D cell-cell interaction. It was difficult to extract spheroids using conventional microchips and fixed cell trapping barriers. The proposed chip, however, facilitates both formation and extraction of spheroids by using removable cell trapping barriers formed by membrane deflection. The cell trapping barriers, formed at the membrane pressure of 50 kPa, hold the cells in the trapping region at a cell inlet pressure of 145.155 Pa. After incubation for 24 h, the trapped cells form uniform spheroids. We successfully extract the spheroids at a cell inlet pressure of 5 kPa after removing the membrane pressure. The extracted spheroids have a diameter of $197.2{\pm}11.7Bm$ with a viability of $80.3{\pm}7.7%$. Using the proposed chip, uniform spheroids can be formed and these spheroids can be safely extracted for carrying out the post-processing of spheroids.

• Journal of Korean Neurosurgical Society
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• v.60 no.5
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• pp.604-609
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• 2017

Objective : An adjustable Ghajar guide is presented to improve the accuracy of the original Ghajar guide technique. The accuracy of the adjustable Ghajar guide technique is also investigated. Methods : The coronal adjustment angle from the orthogonal catheter trajectory at Kocher's point is determined based on coronal head images using an electronic picture archiving and communication system. For the adjustable Ghajar guide, a protractor is mounted on a C-shaped basal plate that is placed in contact with the margin of a burrhole, keeping the central $0^{\circ}$ line of the protractor orthogonal to the calvarial surface. A catheter guide, which is moved along the protractor and fixed at the pre-determined adjustment angle, is then used to guide the ventricular catheter into the frontal horn adjacent to the foramen of Monro. The adjustable Ghajar guide technique was applied to 20 patients, while a freehand technique based on the surface anatomy of the head was applied to another 47 patients. The accuracy of the ventricular catheter placement was then evaluated using postoperative computed tomography scans. Results : For the adjustable Ghajar guide technique (AGT) patients, the bicaudate index ranged from 0.23 to 0.33 ($mean{\pm}standard$ deviation [SD] : $0.27{\pm}0.03$) and the adjustment angle ranged from $0^{\circ}$ to $10^{\circ}$ ($mean{\pm}SD:5.2^{\circ}{\pm}3.2^{\circ}$). All the AGT patients experienced successful cerebrospinal fluid diversion with only one pass of the catheter. Optimal placement of the ventricular catheter in the ipsilateral frontal horn approximating the foramen of Monro (grade 1) was achieved in 19 patients (95.0%), while a suboptimal trajectory into a lateral corner of the frontal horn passing along a lateral wall of the frontal horn (grade 3) occurred in 1 patient (5.0%). Thus, the AGT patients experienced a significantly higher incidence of optimal catheter placement than the freehand catheterized patients (95.0% vs. 68.3%, p=0.024). Moreover, none of the AGT patients experienced any tract hemorrhages along the catheter or procedure-related complications. Conclusion : The proposed adjustable Ghajar guide technique, using angular adjustment in the coronal plane from the orthogonal trajectory at Kocher's point, facilitates accurate freehand placement of a ventricular catheter for hydrocephalic patients.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.1
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• pp.37-44
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• 2019

A bond-based peridynamic model has been reported dynamic fracture characteristic of brittle materials through a simple constitutive model. In the model, each bond is assumed to be a simple spring operating independently. As a result, this simple bond interaction modeling restricts the material behavior having a fixed Poisson's ratio of 1/4 and not being capable of expressing shear deformation. We consider a state-based peridynamics as a generalized peridynamic model. Constitutive models in the state-based peridynamics are corresponding to those in continuum theory. In state-based peridynamics, thus, the response of a material particle depends collectively on deformation of all bonds connected to other particles. So, a state-based peridynamic theory can represent the volume and shear changes of the material. In this paper, the perfect plasticity is considered to express plastic deformation of material by the state-based peridynamic constitutive model with perfect plastic flow rule. The elastic-plastic behavior of the material is verified through the stress-strain curves of the flat plate example. Furthermore, we simulate the high-speed impact on 3D granite model with a nonlocal contact modeling. It is observed that the damage patterns obtained by peridynamics are similar to experimental observations.

• Korean Journal of Heritage: History & Science
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• v.43 no.3
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• pp.102-121
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• 2010

Three bronze bells excavated from the Hoeamsa temple site were investigated for their microstructures and chemical compositions in an effort to understand the technology applied in fabrication, which may represent the related industry established in the early Joseon period. The result shows that the bells were cast from alloys of approximately 85% copper-8% tin-7% lead. The chemical analysis for ten trace elements shows that they were all kept below 0.3 weight %, suggesting that the alloys were made of relatively well-refined copper, tin and lead. The presence of sulfur and iron indicates that chalcopyrite or chalcocite may have been used in the smelting of copper. Evidence has been found that the bells were cast by pouring the liquid metal from the top of the sand molds that were set up in an upright position. No additional treatments, thermal or mechanical, other than a little grinding were applied upon the completion of casting. After the shaping process, a balancing plate was attached to the top of the bell using a steel connection ring. The connection assembly was then fixed to the main body by using molten bronze as a solder. The surface inscription was found carved using different techniques. The differences in the order of strokes and the calligraphic style indicate that the carving was carried out by more than one master. In the absence of documentary evidence on past bronze technology, the present bronze bells with known chronology, provenance and the main agent of production, prove to be a rare and valuable archaeological material for the understanding of the related technology in use in the early Joseon period.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.1
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• pp.30-48
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• 2019

The year 2018 is the $50^{th}$ anniversary of scientific ocean drilling. Nevertheless, we know more about the surface of the moon than the Earth's ocean floor. In other words, there are still no much informations about the Earth interior. Much of what we do know has come from the scientific ocean drilling, providing the systematic collection of core samples from the deep seabed. This revolutionary process began 50 years ago, when the drilling vessel Glomar Challenger sailed into the Gulf of Mexico on August 11, 1968 on the first expedition of the federally funded Deep Sea Drilling Project (DSDP). DSDP followed successively by Ocean Drilling Program (ODP), Integrated Ocean Drilling Program (old IODP), and International Ocean Discovery Program (new IODP). Concerning on the results of scientific ocean drilling, there are two technological innovations and various scientific research results. The one is a dynamic positioning system, enables the drilling vessel to stay fixed in place while drilling and recovering cores in the deep water. Another is the finding of re-entry cone to replace drill bit during the drilling. In addition to technological innovation, there are important scientific results such as confirmation of plate tectonics, reconstruction of earth's history, and finding of life within sediments. New IODP has begun in October, 2013 and will continue till 2023. IODP member countries are preparing for the IODP science plan beyond 2023 and future 50 years of scientific ocean drilling. We as IODP member also need to participate in keeping with the international trend.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.3
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• pp.167-171
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• 2004

The growth of soybean sprout was greatly influenced by watering systems： Fixed watering system (water tub was loaded at ceiling upper of culture box and water was showered by bottom holes) was estimated the better than that of reciprocating watering and tub immersing watering because it could cool down the temperature in culture box and wash the organic substances on the body of sprout. The fixed watering system showed good body color and preventing effect of partial rotting of sprout because it could discharge $\textrm{CO}_2$ gas effectively in culture box and keep the concentration below 5%. The concentration of gases at the bottom (about 30 cm height from basal plate) of culture box in fourth or fifth days was L6% for $\textrm{CO}_2$ and 13-16% for $\textrm{O}_2$, respectively. The optimum gas concentration in culture box was considered to be over 10% for $\textrm{O}_2$ and below 5% for $\textrm{CO}_2$.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.4
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• pp.294-300
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• 2010

Purpose: The template-guided implant surgery offers several advantages over the traditional approach. The purpose of this study was to evaluate the accuracy of coordinate synchronization procedure with 5-axis milling machine for surgical template fabrication by means of reverse engineering through universal CAD software. Materials and methods: The study was performed on ten edentulous models with imbedded gutta percha stoppings which were hidden under silicon gingival form. The platform for synchordination was formed on the bottom side of models and these casts were imaged in Cone beam CT. Vectors of stoppings were extracted and transferred to those of planned implant on virtual planning software. Depth of milling process was set to the level of one half of stoppings and the coordinate of the data was synchronized to the model image. Synchronization of milling coordinate was done by the conversion process for the platform for the synchordination located on the bottom of the model. The models were fixed on the synchordination plate of 5-axis milling machine and drilling was done as the planned vector and depth based on the synchronized data with twist drill of the same diameter as GP stopping. For the 3D rendering and image merging, the impression tray was set on the conbeam CT and pre- and post- CT acquiring was done with the model fixed on the impression body. The accuracy analysis was done with Solidworks (Dassault systems, Concord, USA) by measuring vector of stopping’s top and bottom centers of experimental model through merging and reverse engineering the planned and post-drilling CT image. Correlations among the parameters were tested by means of Pearson correlation coefficient and calculated with SPSS (release 14.0, SPSS Inc. Chicago, USA) ($\alpha$ = 0.05). Results: Due to the declination, GP remnant on upper half of stoppings was observed for every drilled bores. The deviation between planned image and drilled bore that was reverse engineered was 0.31 (0.15 - 0.42) mm at the entrance, 0.36 (0.24 - 0.51) mm at the apex, and angular deviation was 1.62 (0.54 - 2.27)$^{\circ}$. There was positive correlation between the deviation at the entrance and that at the apex (Pearson Correlation Coefficient = 0.904, P = .013). Conclusion: The coordinate synchronization 5-axis milling procedure has adequate accuracy for the production of the guided surgical template.

• Journal of radiological science and technology
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• v.33 no.3
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• pp.261-268
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• 2010

This study is compared that the dose distribution by experimentation and radiation therapy planning (RTP) when the air cavity region was treated high energy photon. The dose measurements were performed with a 6 MV photon beam of linear accelerator. The polystyrene and self made acyl phantom were similar to tissue density of the human body. A parallel plate chamber was connected to an electrometer. The measurement setup was SCD (Source Chamber Distance) 100 cm and the distance of surface from air cavity was 3 cm. Absorbed dose of interface were measured by area and height. The percent depth dose were measured presence and absence of air cavity, depth according to a ratio of field size and air cavity size. The dose distribution on planning was expressed to do the inhomogeneity correction. As the area of air cavity was increased, the absorbed dose were gradually reduced. It was slightly increased, when the height of air cavity was changed from 0 cm to 0.5 cm. After the point, dose was decreased. In case of presence of air cavity, dose after distal air cavity interface was more great than absence of air cavity. The rebuild up by field size and area of air cavity occurred for field size, $4{\times}4\;cm^2$, $5{\times}5\;cm^2$ and $6{\times}6\;cm^2$, with fixed on area of air cavity, $5{\times}5\;cm^2$. But it didn't occur at $10{\times}10\;cm^2$ field size. On the contrary, the field size was fixed on $5{\times}5\;cm^2$, rebuild up occurred in area of air cavity, $4{\times}4\;cm^2$, $5{\times}5\;cm^2$. but, it did not occur for air cavity, $2{\times}2\;cm^2$, $3{\times}3\;cm^2$. All of the radiation therapy planning were not occurred rebuild up. It was required to pay attention to treat tumor in air cavity because the dose distribution of planning was different from the dose distribution of patient.

• Korean Journal of Heritage: History & Science
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• v.54 no.3
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• pp.4-23
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• 2021

The purpose of this study was to classify the types of tweezers used across time and to examine the social culture of periods through the use of tweezers. Chapter II summarized the terms for tweezers and looked at the use of tweezers in two cases related to the social culture and politics of a period. The first is the use of tweezers for beauty purposes. Men used tweezers as a kind of self-management to maintain their social status and power, and thus they helped develop a wide range of tweezers cultures. People with gray hair are usually old. The perception that we should step down from politics when we are aged has become strong. Therefore, politicians pulled out gray hairs with tweezers to maintain only black hair and show youth, which indicates that their social influence is still strong. The second is the use of tweezers for first aid. Chapter III classified tweezers by type during the Goryeo and Joseon periods. The tweezers are largely divided into basic and composite types. The basic type of tweezers is a form that has been continued since the Three Kingdoms Period and consists of tongs and handles, and a fixed type of tweezers with a fixed ring appeared. Composite tweezers are made by grafting earpick or multipurpose knives. Composite tweezers are all-in-one tweezers with an earpick and an all-in-one knife. Tweezers are usually all-in-one. Among the composite tweezers, rivet separation and ring separation are characterized by separation, unlike the all-in-one tweezers. The method of connecting is divided into rivets and connection rings. The all-in-one tweezers appear only during the Goryeo Dynasty and are characterized by the lifestyle that provides a glimpse of the tastes of contemporary users. The manufacturing takes shape after making a thin metal plate. Decorative techniques are carved on soft metal tweezers, such as silver and bronze with a line, point, and a pressed angle. These tweezers are presumed to have been used by the royal family or aristocrats. However, most tweezers are made of strong bronze or iron. Therefore, the majority of simple X-shaped patterns are sampled or without patterns. The biggest reason why there are such diverse types of tweezers is that the culture of tweezers was widespread regardless of the times. In addition, the basic type of tweezers has been used since the Three Kingdoms Period and has been modified and used together as necessary because the shape of tweezers is a practical daily tool. Study of metal crafts have been limited to royal objects and Buddhist crafts. We hope that research on everyday tools such as tweezers will continue to serve as an opportunity to examine the social and cultural aspects of the times in various ways.

• Journal of Veterinary Clinics
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• v.22 no.4
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• pp.336-341
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• 2005

Anabolic steroid compounds are widely used for the increase of muscle mass, density of bone and athletic ability. The present study conducted to evaluate the effects of nandrolone decanoate (ND), one of the anabolic steroid compounds, on disuse muscle atrophy and healing process of bone in dogs. Twenty physically healthy dogs of both sexes were used in this experiment and divided into three groups: group A (control), group B (low dose M-1.5 mg/kg) and group C (high dose ND-7.5 mg/kg). One-mm strip of full thickness bone was excised from the radius below the pronator teres muscle for the artificial fracture and then the fractured ends were fixed in apposition with bone plate leaving 1mm gap, and finally immobilized externally by Robert John's bandage for 4 weeks. ND was administered intramuscularly once a week far 8 weeks. Body weight, muscle mass change and fracture gap of the bone were evaluated immediately after surgery, and 2, 4, and 8 weeks after surgery. The rates of muscle mass change 8 weeks after surgery were $-2.75\pm0.16\%,\;1.68\pm0.11\%\;and\;1.74\pm0.48\%$ in groups A, B and C, respectively. The significant increase (p<0.05) of muscle mass increments were found in the treated groups. The fibrous connective tissue layer in the fracture gaps of the treated groups increased more than the control, especially in the group C at 4th week. More dense fibrous connective tissue were found in the treated groups at 8th week. Collectively, our results suggested that ND was an effective anabolic agent for the immobilized disuse muscle and bone healing.