• Korean Chemical Engineering Research
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• 제48권1호
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• pp.103-109
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• 2010

하폐수 처리과정에서 발생되는 슬러지는 주로 혐기소화에 의해 처리되며 슬러지를 감량하고 메탄을 생산할 수 있어 많이 이용되고 있다. 슬러지의 전처리는 혐기소화의 율속단계인 가수분해를 높여 처리속도를 향상시키므로 많은 연구가 진행 중이다. 본 연구에서는 열, 초음파, 열-알칼리의 전처리 기술에 따른 슬러지의 가수분해(가용화) 효과와 전처리한 슬러지를 혐기소화하여 메탄 생산량과 슬러지의 감량 효과를 비교하였다. 하수와 폐수 슬러지 가용화율은 열-알칼리 동시 처리한 경우에는 67과 70%로 가장 높았고 다음으로 초음파 처리와 열처리가 40% 이상의 비슷한 가용화율을 보였다. 혐기소화 가스의 메탄 함량은 45~70% 범위로 유지되었고 전처리한 슬러지가 control에 비해 높게 나타났다. 메탄 생산량은 열처리, 초음파 처리, 열-알칼리를 같이 처리한 경우가 control에 비해 각각 하수슬러지는 2.6, 2.7, 3.5배, 폐수 슬러지는 3.5, 4.1, 4.2배 증가하였다. 혐기소화 슬러지의 감량효과는 전처리한 슬러지가 control에 비해 5~19% 포인트 높게 나타났으며 열-알칼리 처리한 경우가 초음파와 열처리에 비해 우수한 감량 효과를 보였다. 위의 결과로부터 전처리가 메탄 생산량에서 뿐만 아니라 슬러지 처리처분 비용 절감에 있어서도 중요한 역할을 함을 확인할 수 있었고 열-알칼리 동시 처리가 가장 우수한 성능을 보였다.

• 한국멀티미디어학회논문지
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• 제25권8호
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• pp.1038-1048
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• 2022

Ultrasound is one of the effective methods for skin treatment. The skin penetration depth of the ultrasound depends on the ultrasonic frequency, that is, when the ultrasonic frequency is high, the depth is shallow. We have developed a transducer which can generate effectively 3 different ultrasonic frequencies removing interference between 3 types of frequencies according to impedance matching technology. The generated powers of transducer are 40.67W at 3.MHz, 17.46W at 11.7 MHz, and 14.79W at 21.5 MHz. The signal interference between the three frequencies is designed so that they do not interfere with each other by separating the signals using the SPDT (Single Pole, Double Throw) switch. The developed hybrid ultrasound transducer can be applied in skin care or skin treatment and beauty therapy.

• 한국정밀공학회지
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• 제31권12호
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• pp.1115-1119
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• 2014

In this article, a 20 kHz ultrasonic waveguide for nano-surface treatment was designed and manufactured. When designing the system, finite element analysis with ANSYS software was performed to find optimal dimensions of the waveguide, which can raise energy efficiency. Consequently an anti-resonance frequency of an Al waveguide with a piezoelectric actuator was 20 kHz, which predicted the experimentally obtained value of 18 kHz well. For the assessment of the performance, Steel Use Stainless (SUS) 304 and chromium molybdenum steel (SCM) 435 specimens were tested. Cross-sectional microscopies of SUS304 were taken and they showed that the treated thickness was $30{\mu}m$. Additionally, hardness tests of SCM435 were done and the hardness before the process was 14.0 Rockwell Hardness-C scale (HRC) and after the process was 20.5 HRC, respectively, which means 46% increase. Considering these results, the developed ultrasonic system is thought to be effective in the nano-surface treatment process.

• 전기학회논문지
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• 제57권5호
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• pp.803-807
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• 2008

A making process of DSC(dye sensitized solar cell) was presented. In general, Photo electrodes of DSC was made by using colloid paste of nano $TiO_2$ and processing of Doctor-blade printing and high temperature sintering for porous structure. These methods lead to cracks on $TiO_2$ surface and ununiform of $TiO_2$ thickness. This phenomenon is one factor that makes low efficiency to cells. After $TiO_2$ printing on TCO glass, a physical vibration was adapted for reducing ununiform of $TiO_2$ thickness. And a thermal treatment at low temperature(under $75^{\circ}C$) was adapted for reducing cracks on $TiO_2$ surface. In this paper, we have designed and manufactured an ultrasonic circuit (100W, frequency and duty variable) and a thermal equipment. Then, we have optimized forcing time, frequency and duty of ultrasonic irradiation and thermal heating for surface treatment of photo-electrode of DSC. In I-V characteristic test of DSC, ultrasonic and thermal treated DSC shows 19% improved its efficiency against monolithic DSC. And it shows stability of light-harvesting from drastically change of light irradiation test.

• 한국생산제조학회지
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• 제23권1호
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• pp.48-55
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• 2014

Many techniques are available for destructive and nondestructive measurement of mechanical hardness. The ultrasonic method could be widely applicable as a nondestructive technique. Many studies have examined how changes in the mechanical hardness affect the longitudinal velocity of ultrasonic waves. This approach aims to estimate the overall velocity variations in specimens. However, proper nondestructive examination techniques are needed as effective tools for analyzing the effects of heat treatment on the surface of the specimens. Therefore, in this study, the effect on the hardness of piston rods was nondestructively measured using surface ultrasonic waves. The hardness after heat treatment was investigated at various depths in the specimens, and the velocity of the surface ultrasonic waves was measured with respect to the hardness of the piston rods. In addition, finite element method simulations were performed to confirm the behavior of the waves.

• 치위생과학회지
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• 제23권2호
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• pp.176-184
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• 2023

Background: Recently, a piezoelectric ultrasonic scaler based on a feedback control mechanism was introduced for pain relief. This study aimed to investigate the effects of a new ultrasonic scaler in reducing pain and discomfort in adults. Methods: A newly introduced ultrasonic scaler (Master 700^®) was used as the test device and a conventional ultrasonic scaler device (PIEZON^®) was used as the control device. Forty-one healthy adults visited the dental clinic for dental scaling but did not undergo scaling or periodontal treatment within 6 months. Intraoral examinations were performed before scaling and 3 months later; before scaling, both devices were randomly assigned on the left or right side of each dentition (split-mouth model) and scaling was performed by a registered dental hygienist. The levels of pain and discomfort during scaling were evaluated subjectively and objectively using the visual analog scale (VAS) and physiological monitoring of the heart rate (HR), respectively. Time was measured for each device. Results: All clinical indicators, except bleeding on probing, significantly improved with both devices. The treatment times were 7 minutes, 13 minutes (control) and 6 minutes, 59 minutes (test). VAS scores for pain were 4.89±2.12 (control) and 4.58±2.77 (test) points out of 10; for noise, these were 4.68±2.33 (control) and 4.55±2.55 (test), and for vibration, the values were 4.26±2.0 (control) and 4.18±2.48 (test). HR averages were 72.34±3.39 (control) and 75.97±9.78 (test) beats/min. No statistically significant differences were observed between the devices. Conclusion:The pain, discomfort levels, and scaling time of the new piezoelectric ultrasonic scaler did not differ from those of the conventional device. Further research and development are necessary for more prominent pain-relief effects of scaling devices.

• 접착 및 계면
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• 제14권3호
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• pp.146-159
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• 2013

본 연구에서는 $350^{\circ}C$에서 4 min 이내로 빠르게 등온 안정화공정을 통해 얻어진 레이온직물의 화학조성, 물리적 특성, X-선 회절 패턴, 열안정성 그리고 직물 형상에 미치는 초음파세척 및 화학전처리의 영향을 조사하였다. 안정화공정 동안 레이온직물에서 발생하는 중량감소와 열수축을 줄이고 안정화반응을 촉진시키기 위하여 안정화공정 전에 레이온직물을 먼저 초음파 세척하고 $NH_4Cl$, $Na_3PO_4$, $H_3PO_4$ 및 $ZnCl_2$로 화학전처리 공정을 수행하였다. 결과는 초음파세척 및 화학전처리가 안정화된 레이온직물의 중량감소, 열수축, 미세구조 변화, 탄소함량, 열안정성, 및 직물 형상에 영향을 주었으며, 사용한 안정화시간과 화학전처리제의 종류에 의존하였다.

• 마이크로전자및패키징학회지
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• 제10권4호
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• pp.65-71
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• 2003

압전 세라믹스를 이용하여 약품 분사용 초음파분사 노즐을 제작하였다. 정수장의 혼화 공정에 사용되는 약품(응집제)의 고효율 분산을 위해 분사 노즐을 설계하였으며 압전세라믹을 최적화하였다. 제작된 초음파 약품 분사 노즐을 패키징하여 정수장의 약품 혼화 과정에 적용하여 약품사용의 고 효율화와 사용량 저감을 위한 연구를 진행하였다. 압전체는 실리콘으로 마감처리를 하였으며 Al으로 패키징하였다. 본 초음파 분사 노즐 시스템을 적용하여 혼화지에 실험한 결과 약품의 순간 혼화를 촉진시키는 기술로 투입 약품량을 저감시킬 수 있을 것으로 판단된다. 초음파 발진 약품 분사시, 무발진과 비교하여 대장균 제거 효율에서 현저하게 높아졌다.

• Journal of Periodontal and Implant Science
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• 제38권4호
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• pp.657-668
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• 2008

Purpose: In this study, we compared low-power $CO_2$ laser treatment to ultrasonic scaling, which is generally approved as a power-driven mechanical instrumentation, and evaluated both of these treatments regarding their clinical effectiveness and change in the volume of in GCF. Material and methods: 20 patients who had gingivitis were selected. all of patients has no systemic problems. Randomly selected, one quadrant received ultrasonic scaling only, another quadrant received ultrasonic scaling and $CO_2$ laser irradiation, the other quadrant received $CO_2$ laser irradiation only. Clinical parameters measured at baseline, 1 weeks, 2weeks, 4weeks and 8weeks. Result: Pocket probing depth and clinical attachment level were not changed during study period. Gingival index of all group were improved after treatment. At 1 weeks after treatment, Gingival index of ultrasonic scaling group was only significantly different compared to control group. At 2 weeks after treatment, gingival index of all experimental group were significantly different compared to control group. At 4 and 8 weeks after treatment, gingival index of all group were increased, but experimental group were lower than control group. Sulcus bleeding index was similar to the results of gingival index. At 1 weeks after treatment, all experimental group were significantly different compared to control group and it maintained during study. At 2 weeks after treatment, sulcus bleeding index of all group were lowest during study. Gingival crevicular fluid were measured with $Periotron^{(R)}$ 8000($Oraflow^{(R)}$, Inc. USA). At baseline, all group were showed moderately severe condition. At 1 week after treatment, laser treatment only group was reduced quantity of gingival crevicular fluid mostly, and all group were reduced quantity of gingival crevicular fluid. At 2 weeks after treatment, all group were health state. At 4 and 8 weeks after treatment, all group were showed recurrent of inflammation, and control group was the most significantly increased. Conclusion: This study showed that the effects of $CO_2$ laser treatment were similar to conventional ultrasonic scaling and this result remained longer than plaque control only. These results suggest possibility of $CO_2$ laser treatment for altered periodontal therapy.

• Journal of Periodontal and Implant Science
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• 제39권3호
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• pp.303-310
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• 2009

Purpose: The aerosol generated by ultrasonic scaler can contain bacteria or virus which can penetrate into body through respiratory systems of dentists, dental hygienist or patients. The aim of this study is to evaluate the effect of chlorhexidine digluconate as preoperative mouthrinse or lavage for ultrasonic scaler on the reduction of viable organisms in aerosol produced during periodontal treatment using ultrasonic scaler. Methods: 30 patients with moderate chronic periodontitis were included and divided into 3 groups: Control (no preoperative mouthrinse and tap water as lavage), CHG (preoperative mouthrinse with 0.1% chlorhexidine digluconate and tap water as lavage), CHL (no preoperative mouthrinse and 0.1% chlorhexidine digluconate as lavage). Each patient received scaling or subgingival curettage for 30 min. In CHG group, mouthrinse with chlorhexidine digluconate was performed for 1 min. before treatment. Before, during and after scaling or subgingival curettage, air sampling was performed for 7 min. each (1000 L/7 min.) with trypticase-soy agar plate. Agar plates were incubated in $37^{\circ}C$ aerobically. The numbers of colony-forming units (CFU) were counted and compared. Results: The numbers of CFUs of the samples obtained during treatment were $97{\pm}14.0$ in control, $73.1{\pm}14.9$ in CHG group and $44.5{\pm}9.0$ in CHL group. The difference among the 3 groups was determined to be statistically significant (one-way ANOVA with Bonferroni's correction, p-value: 0.0003). In contrast, the numbers of CFU of samples obtained before and after treatment were not significantly different among the groups. Conclusions: Chlorhexidine digluconate used as preoperative mouthrinse or lavage for ultrasonic scaler can reduce the microorganisms in aerosol produced during periodontal treatment using ultrasonic scaler. Less number of microorganisms were detected when chlorhexidine was used as lavage for ultrasonic scaler.