• The korean journal of orthodontics
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• 제43권4호
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• pp.186-192
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• 2013

Objective: To analyze the fatigue resistance, debonding force, and failure type of fiber-reinforced composite, polyethylene ribbon-reinforced, and braided stainless steel wire lingual retainers in vitro. Methods: Roots of human mandibular central incisors were covered with silicone, mimicking the periodontal ligament, and embedded in polymethylmethacrylate. The specimens (N = 50), with two teeth each, were randomly divided into five groups (n = 10/group) according to the retainer materials: (1) Interlig (E-glass), (2) everStick Ortho (E-glass), (3) DentaPreg Splint (S2-glass), (4) Ribbond (polyethylene), and (5) Quad Cat wire (stainless steel). After the recommended adhesive procedures, the retainers were bonded to the teeth by using flowable composite resin (Tetric Flow). The teeth were subjected to 10,00,000 cyclic loads (8 Hz, 3 - 100 N, $45^{\circ}$ angle, under $37{\pm}3^{\circ}C$ water) at their incisoproximal contact, and debonding forces were measured with a universal testing machine (1 mm/min crosshead speed). Failure sites were examined under a stereomicroscope (${\times}40$ magnification). Data were analyzed by one-way analysis of variance. Results: All the specimens survived the cyclic loading. Their mean debonding forces were not significantly different (p > 0.05). The DentaPreg Splint group (80%) showed the highest incidence of complete adhesive debonding, followed by the Interlig group (60%). The everStick Ortho group (80%) presented predominantly partial adhesive debonding. The Quad Cat wire group (50%) presented overlying composite detachment. Conclusions: Cyclic loading did not cause debonding. The retainers presented similar debonding forces but different failure types. Braided stainless steel wire retainers presented the most repairable failure type.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제8권1호
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• pp.33-40
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• 1988

The new technique has been used to determine the soil-reinforcement interaction. The testing apparatus is essentially a triaxial cell fitted with the capability to house a hollow cylinderical sample. A hollow cylinderical sand specimen with a concentrical layer of reinfarcing material sandwitched in the middle is used in this investigation. The reinforcement is fastened at the base. The hollow specimen can be viewed as a "unit sheet" of a soil-reinforcement composite system of infinite horizontal extent. Axial load as well as inner and outer chamber pressures can be applied to perform a test. The specimen is first subjected to an isotropic stress state corresponding to the overburden pressure. Next, an extension test by reducing the axial load is carried out. The specimen is "loaded" to failure by either the breakage of reinforcing material (tensile failure) or slippage which takes place at the soil-reinforcement interface (i.e. the overcoming of the bonding capacity). Since the reinforcement is fastened at its lower end to the base, any tendency of relative movement between the reinforcement and the sand during an extension test can induce tensile force in the reinforcement thus forming a "reversed pull-out" test condition. Preliminary test results have demonstrated positively of the new approach to test the soil-reinforcement interaction. Reinforcing elements of different extensibility were used to study the deformbility of reinforced soil. Furthermore, both the breakage and the pull-out modes of failure were observed.

• Proceedings of the KSME Conference
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• 대한기계학회 2004년도 추계학술대회
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• pp.1196-1200
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• 2004

Micropump is very useful component in micro/nano fluidics and bioMEMS applications. In this study, a bubble-powered micropump was fabricated and tested. The micropump consists of two-parallel micro line heaters, a pair of nozzle-diffuser flow controller and a 1 mm in diameter, 400 ${\mu}m$ in depth pumping chamber. The two-parallel micro line heaters with 20 ${\mu}m-width$ and 200 ${\mu}m-length$ were fabricated to be embedded in the silicon dioxide layer of a wafer which serves as a base plate for the micropump. The pumping chamber, the pair of nozzle-diffuser unit and microchannels including the liquid inlet and outlet port were fabricated by etching through another silicon wafer. A glass wafer (thickness of $525{\pm}15$ ${\mu}m$) having two holes of inlet and outlet ports of liquid serve as upper plate of the pump. Finally the silicon wafer of the base plate, the silicon wafer of pumping chamber and the glass wafer were aligned and bonded (Si-Si bonding and anodic bonding). A sequential photograph of bubble nucleation, growth and collapse was visualized by CCD camera. Clearly liquid flow through the nozzle during the period of bubble growth and slight back flow of liquid at the end of collapsing period can be seen. The mass flow rate was found to be dependent on the duty ratio and the operation frequency. As duty ratio increases, flow rate decreases gradually when the duty ratio exceeds 60%. Also as the operation frequency increases, the flow rate of the micropump decreases slightly.

• Korean Journal of Organic Agriculture
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• 제28권3호
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• pp.367-386
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• 2020

The significance of this study was to analyze the quality value of organic livestock pork for the first time based on the results of managing and testing the cycling organic farming of black pork and vegetables within farm for two years. The results of analysis could be summarized as follows. First, the pork of experimental group with crop-livestock cycling farming showed the excellent quality and high consumer preference compared to the control group of general pork or pork from non-crop-livestock cycling organic farming. In the content ratio of Omega-3 as a representative essential fatty acid, it was 1.46 that was about 2.8 times more than general pork (0.52). In case of Omega-6, it had about 2.5 times more than general pork. Especially, the U/S ratio value which was the content ratio of Unsaturated Fatty Acid (UFA, U) of Saturated Fatty Acid (SFA, S), was largely shown in pork (2.93) from cycling organic farming. Second, it would be necessary to maintain the economies of scope shown in crop-livestock cycling organic farming, and the high quality value of livestock products. For this, there should be a value chain model that could realize the economies of scope and economies of scale at the same time based on scaling and diversification through cooperative organization between farmers. Through this, it would be possible to establish a cycling model called 'community cooperative agriculture' by forming local internal markets through cooperation of production-processing and integration of distribution-sale-consumption. For the managerial activation of this cooperative organization, the government should promote/support the small crop-livestock cycling organic farming cooperative organization in local unit. For securing the reliability of crop-livestock cycling organic agricultural products and crop-livestock cycling organic livestock products, it would be necessary to review the introduction of Participatory Guarantee System (PGS).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.489-493
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• 2005

TFT-LCD(Thin Film Transistor Liquid Crystal Display) module is representative commercial product of FPD(Flat Panel Display). Thickness of TFT-LCD module is very thin. It is adopted for major display unit for IT devices such as Cellular Phone, Camcorder, Digital camera and etc. Due to the harsh user environment of mobile IT devices, it requires complicated structure and tight assembly. And user requirements for the mechanical functionalities of TFT-LCD module become more strict. However, TFT-LCD module is normally weak to high level transient mechanical shock. Since it uses thin crystallized panel. Therefore, anti-shock performance is classified as one of the most important design specifications. Traditionally, the product reliability against mechanical shock is confirmed by empirical method in the design-prototype-drop/impact testredesign paradigm. The method is time-consuming and expensive process. It lacks scientific insight and quantitative evaluation. In this article, a systematic design evaluation of TFT-LCD module for mobile IT devices is presented with combinations of FEA and testing to support the optimal shock proof display design procedure.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 한국근적외분광분석학회 2001년도 NIR-2001
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• pp.4111-4111
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• 2001

When a drug is prepared in a tablet, the active component represents only a small portion of the dosage form. The other components of the formulation include materials to assist in the dissolution, antioxidants, coloring agents and bulk fillers. The tablets are tested using approved testing methods usually involving separation and subsequent quantification of the active component. Tablets may also be tested by near-Infrared Reflectance spectrometry (NIRS). In the present study, based on NIRS and multivariate calibration methods, a novel and precise method is developed for direct determination of ascorbic acid in vitamin C tablet. Two different tablet formulations were powdered in three different sizes, 63-125 ${\mu}{\textrm}{m}$, and examined. Spectral region of 4750-4950 $cm^{-1}$ / was used and optimized for quantitative operations. Partial least squares (PLS) and multiple linear regression (MLR) methods were performed for this spectral region. The results of optimized PLS and MLR methods showed that reproducibility increase with decreasing grain size and standard error of calibration (SEP) of less than 1% w/w of ascorbic acid and a correlation coefficient of 0.998 can be achieved. The PLS method showed better results than MLR. Seven overdose and underdose samples (prepared in the laboratory to match marketed products) were tested by proposed and iodometric standard methods. A correlation between NIRS predicted ascorbic acid values and iodomet.ic values was calculated ($R^2$=0.9950). Finally, the direct analysis of individual intact tablets in their unit-dose packages (Blistering in aluminum and PVC foils) obtained from market were also carried out and a correlation coefficient of 0.9989 and SEP of 0.931% w/w of ascorbic acid were achieved.

• Journal of the Korea Institute of Military Science and Technology
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• 제23권6호
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• pp.639-649
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• 2020

Air data systems measure airspeed, pressure altitude, angle of attack and angle of sideslip. These measurements are essential for operating flight control laws to ensure safe flights. Since the loss or corruption of air data measurements is considered as catastrophic, a high level of operational reliability needs to be achieved for air data systems. In the case of unmanned air vehicles, failure of any of air data sensors is more critical due to the absence of onboard pilot decision aid. This paper presents design of a dual redundancy air data system and the integration process for an unmanned air vehicle. The proposed dual-redundant architecture is based on two independent air data probes and redundancy management by central processing in two independent flight control computers. Starting from unit testing of single air data sensor, details are provided of system level tests used to meet overall requirements. Test results from system integration demonstrate the efficiency of the proposed process.

• Atmosphere
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• 제17권4호
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• pp.339-348
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• 2007

Global Environment Laboratory at Yonsei University in Seoul ($37.57^{\circ}N$, $126.95^{\circ}E$) has carried out the ozone layer monitoring program in the framework of the Global Ozone Observing System of the World Meteorlogical Organization (WMO/GAW/GO3OS Station No. 252) since May of 1984. The daily measurements of total ozone and the vertical distribution of ozone amount have been made with the Dobson Spectrophotometer (No.124) on the roof of the Science Building on Yonsei campus. From 2004 through 2006, major parts of the manual operations are automated in measuring total ozone amount and vertical ozone profile through Umkehr method, and calibrating instrument by standard lamp tests with new hardware and software including step motor, rotary encoder, controller, and visual display. This system takes full advantage of Windows interface and information technology to realize adaptability to the latest Windows PC and flexible data processing system. This automatic system also utilizes card slot of desktop personal computer to control various types of boards in the driving unit for operating Dobson spectrophotometer and testing devices. Thus, by automating most of the manual work both in instrument operation and in data processing, subjective human errors and individual differences are eliminated. It is therefore found that the ozone data quality has been distinctly upgraded after automation of the Dobson instrument.

• Journal of Microbiology and Biotechnology
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• 제26권5호
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• pp.867-875
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• 2016

Archaea substantially contribute to global geochemical cycling and energy cycling and are impacted by land-use change. However, the response of archaeal communities to a change from upland field to paddy field has been poorly characterized. Here, soil samples were collected at two depths (0-20 cm and 20-40 cm) from one upland field and six paddy fields that were established on former upland fields at different times (1, 5, 10, 20, 30, and 40 years before the study). Barcoded pyrosequencing was employed to assess the archaeal communities from the samples at taxonomic resolutions from phylum to genus levels. The total archaeal operational taxonomic unit (OTU) richness showed a significant positive correlation with the land-use change duration. Two phyla, Euryarchaeota and Crenarchaeota, were recorded throughout the study. Both the relative abundance and OTU richness of Euryarchaeota increased at both depths but increased more steadily at the subsurface rather than at the surface. However, these data of Crenarchaeota were the opposite. Additionally, the archaeal composition exhibited a significant relationship with C/N ratios, total phosphorus, soil pH, Olsen phosphorus, and the land-use change duration at several taxonomic resolutions. Our results emphasize that after a change from upland fields to paddy fields, the archaeal diversity and composition changed, and the duration is an important factor in addition to the soil chemical properties.

• Design & Manufacturing
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• 제14권2호
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• pp.21-27
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• 2020

Recently, LCD (Liquid Crystal Display) has been replaced by OLDE (Organic Light Emitting Diode) in high resolution display industry. In the process of OLDE production, it inspects defective products by sending a signal using a probe during OLED panel inspection. At this time, the cause of the detection of failure is divided into two. One is the self-defect of the OLED panel and the other is the poor contact occurring in the process of contact between the two. The second case is unknown at the time of testing, which increases the time for retesting. To this end, we made a system that can identify in real time whether the probe is in contact during the inspection. A contact probe unit was designed for the system, and a stage system was implemented. An inspection system was constructed through S / W and circuit configuration for actual inspection. Finally, a system that can check contact and non-contact in real time was constructed.