Shear strength characteristics of a compacted soil under infiltration conditions

Rahardjo, H.,Meilani, I.,Leong, E.C.,Rezaur, R.B. Techno-Press 2009 Geomechanics & engineering Vol.1 No.1

A significantly thick zone of steep slopes is commonly encountered above groundwater table and the soils within this zone are unsaturated with negative pore-water pressures (i.e., matric suction). Matric suction contributes significantly to the shear strength of soil and to the factor of safety of unsaturated slopes. However, infiltration during rainfall increases the pore-water pressure in soil resulting in a decrease in the matric suction and the shear strength of the soil. As a result, rainfall infiltration may eventually trigger a slope failure. Therefore, understanding of shear strength characteristics of saturated and unsaturated soils under shearing-infiltration (SI) conditions have direct implications in assessment of slope stability under rainfall conditions. This paper presents results from a series of consolidated drained (CD) and shearing-infiltration (SI) tests. Results show that the failure envelope obtained from the shearing-infiltration tests is independent of the infiltration rate. Failure envelopes obtained from CD and SI tests appear to be similar. For practical purposes the shear strength parameters from the CD tests can be used in stability analyses of slopes under rainfall conditions. The SI tests might be performed to obtain more conservative shear strength parameters and to study the pore-water pressure changes during infiltration.

A Review of Indonesia’s Dental Health - Past, Present and Future

Anton Rahardjo,Diah Ayu Maharani 대한예방치과학회 2014 International Journal of Clinical Preventive Denti Vol.10 No.3

Access to dental health care markedly improves citizens’ dental health status, which in turn improves the national quality oflife. This paper aims to review the literatures of the Indonesian Dental Health. All of the related factors that influence dentalhealth were described from 1995 to 2013. Economic and geographic barriers to access dental care still exist in Indonesia. Periodic evaluation on government policy is essential to develop an adequate dental health care system, which then couldimprove outcomes of the national dental health status.

Potential Side Effects of Whitening Toothpaste on Enamel Roughness and Micro Hardness

Anton Rahardjo,Eva Gracia,Grace Riska,Melissa Adiatman,Diah Ayu Maharani 대한예방치과학회 2015 International Journal of Clinical Preventive Denti Vol.11 No.4

Objective: Whitening toothpaste are easily obtained over the counter by consumers. The aim of this study was to assess the side effects of whitening toothpaste on enamel roughness and micro hardness which might contribute to increase caries risk. Methods: Enamel specimens were obtained from 60 unidentified freshly extracted human premolars. The enamel specimens were randomly divided into three groups; whitening toothpaste containing perlite, whitening toothpaste containing e-phtalimido peroxycaproid acid (EURECOⓇ HC, Indonesia), and non-whitening toothpaste as control. Tooth brushing was performed equal to 1 and 3 months. Surface roughness tester was used to determine enamel roughness and Knoop Micro hardness tester was used to determine enamel micro hardness. Results: There were statistically significant differences in enamel roughness after 1 and 3 months equivalent tooth brushing between three groups. There were significant differences in enamel micro hardness values for all groups after three months-brushing which showed a decrease in micro hardness for whitening groups and an increase in micro hardness for non-whitening group. Conclusion: Tooth brushing with whitening toothpaste for a prolonged time increases enamel roughness and decreases enamel micro hardness, which in turn increases the potential of caries risk.

Unsaturated Soil Mechanics for Sustainable Urban Living

김용민,Harianto Rahardjo 한국지반공학회 2017 지반 : 한국지반공학회지 Vol.33 No.4

Unsaturated Soil Mechanics in Engineering Practice

D. G. Fredlund,H. Rahardjo,M. D. Fredlund 대한토목학회 2013 대한토목학회지 Vol.61 No.5

Alumina phase transformation behavior on titania-doped nano α-alumina by a solid liquid process

Rifki Septawendar,Soewanto Rahardjo,Suhanda,Wisnu Hardik Pratomo 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.6

Alumina phase transformation behavior on titania-doped nano α-Al2O3 powder by a solid liquid process was investigated under various conditions, such as different solvent concentrations and calcining temperatures. Three batches of the precursor powders were calcined at three different temperatures of 600 oC, 750 oC and 900 oC for 5 h and a final product of titania-doped nano α-Al2O3 powder was obtained. The product has been identified by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD results show that the alumina phases of the powders were determined to be γ-Al2O3 and α-Al2O3. The optimum calcination temperature of the precursor powder for crystallization of nano α-Al2O3 was found to be 900 oC for 5 h. A higher concentration of solvent used for the sample preparation leads to the formation of a uniform and very smooth particle morphology, and smaller particle grains. The TEM images indicate that the average size of α-Al2O3 grains was ≤ 50 nm and larger grains of TiO2 with 50-250 nm sizes.

Clinical Efficacy of a New Mouthwash Containing Essential Oil of Cardamom in Reducing Volatile Sulphur Coumpounds Concentration

Suci Erawati,Anton Rahardjo,Sondang Pintauli 대한예방치과학회 2014 International Journal of Clinical Preventive Denti Vol.10 No.4

Objective: The aim of this study was to assess the clinical efficacy of new mouthwash based on kapulaga fruit (Amomum cardamommum L.) containing 0.5% essential oil and compared to 0.5% Listerineⓡ as a positive control and placebo in reducing volatile sulphur compounds (VSCs) concentration of halitosis subjects. Methods: A randomized, double blinded, cross-over design was conducted among 20 healthy volunteers in Medan, Indonesia. Subjects were divided into 3 groups (Cardamom, Listerineⓡ, placebo group) and instructed to rinse 10 ml of experiment and control mouthwash twice per day for 5 days. After one week washout periods, each group used the opposite mouthwash. The concentration of VSCs, hydrogen sulfide, methyl mercaptan, and dimethyl sulfide were assessed twice daily for 5 days (morning at 5 a.m. and afternoon at 11 a.m.) by using oral chroma and organoleptic measurement. The three mouthwash were analyzed statistically by repeated measures ANOVA. Results: Either Cardamom or Listerineⓡ was effective in reducing VSCs for up to 4 to 5 hours after mouth rinsing, while placebo not. An analysis showed significant differences of cardamom essential oil in mouthwash and positive control group (p<0.05) from 1st and 5th day while no significant difference in placebo group (p>0.05). Results showed that Cardamom more effective than the other two mouthwashes. Unlike other mouthwash in general, the advantage of cardamom essential oil in mouthwash is alcohol-free, that could avoid from oral pain and sensitivity. Conclusion: It can be concluded that 0.5% cardamom containing essential oil in mouthwash is useful to overcome halitosis.

Efficacy of Mouthwash Containing Curcuma xanthorrhiza on Lactoperoxidase System Activity and Halitosis Risk

Stella Lesmana,Risqa Rina Darwita,Anton Rahardjo 대한예방치과학회 2013 International Journal of Clinical Preventive Denti Vol.9 No.4

Objective: The use of mouthwash may increase the activity of lactoperoxidase system in saliva and may reduce the risk of halitosis. The research was conducted to determine the effect of mouthwash containing Curcuma xanthorrhiza on lactoperoxidase system activity in relation to halitosis risk. Methods: The research design was a before after clinical trial, the 5 ml saliva samples were taken from 10 subjects age 20-23 years oldat 22.00 WIB at night and at 04.00 WIB in the morning. Lactoperoxidase enzyme activity was measured using the method of Chance and Maehly while the concentration of thiocyanate ion was measured using Thomas and Aune method. Results: The mean±SD of the baseline lactoperoxidase activity absorbance in the evening 0.2463333±0.126053 and then decreased in the morning to 0.1994999±0.059258 and the mean±SD baseline thiocyanate ion from 1.9328±0.187181 in the night decreased in the morning to 1.819±0.510573. After intervention with mouthwash containing Curcuma xanthorrhiza, theincreasing of average value of baseline Lactoperoxidase activity absorbances was indicated from 0.2121±0.107991 in the evening becomes 0.240233±0.091862 in the morning, while the average of thiocyanate ion from 1.0531±0.108838 in the evening becomes 1.090267±0.285835 in the morning. There were no significant differences between the activity of lactoperoxidaseenzyme and thiocyanate ion concentrations in both treatments (p>0.05). Conclusion: The use of mouthwash containing Curcuma xanthorrhiza has the potential to raise the lactoperoxidase system activity.

Is Joint Tooth Brushing an Effective Program for Improving Dental Health among Elementary Students? : A Study from Jakarta, Indonesia

R. R. Darwita,Diah Ayu Maharani,A. Rahardjo,D. P. Puspa,R. Amalia,Sandy D. P. 대한임상예방치과학회 2011 International Journal of Clinical Preventive Denti Vol.7 No.3

Objective: To evaluate the effectiveness of a joint tooth brushing program at an elementary school in Jakarta. Methods: An intervention program to improve the oral health of elementary students was conducted over a 6-month period. The program consisted of dental health education and daily indoor two-minute sessions of joint tooth brushing. We sampled a total of 57 students from the first and second grades. Each one was interviewed and was subject to oral examinations before and after the program was implemented. Moreover, questionnaires were also administered to the teachers. Then they were trained as an instructor for the program. These programs were conducted daily before the beginning of class. Results: Significant changes in saliva pH and plaque pH scores was found for students. Moreover, teachers’ awareness of dental healthcare also increased. Finally, teachers were actively engaged when acting as tooth brushing program instructors. Conclusion: Teachers conducting daily, indoor, two-minute, joint tooth brushing programs could motivate students to maintain their oral health. This in turn leads to a decreased prevalence of dental caries among elementary school students.

Influences of Postannealing Treatment Parameters on the Structural and Magnetic Properties of Nickel-Doped Cobalt Ferrite Synthesized by Sol-Gel Route

Sri Budiawanti,R. Amalia,D. T. Rahardjo,Suharno,B. Purnama,D. Djuhana 한국자기학회 2022 Journal of Magnetics Vol.27 No.1

We prepared and characterized nickel-substituted cobalt ferrite (Ni0.1Co0.9Fe₂O₄) nanoparticles using the sol-gel method. The physical properties of the nanoparticles have been modified by postannealing treatment at atmospheric conditions. X-ray diffraction results confirmed that the nanoparticles possessed a single-phase face-centered cubic crystalline structure. The crystallite sizes increased from 20.85 to 26.06 nm with the increased annealing temperature. Transmission electron microscopy results confirmed the crystal structure of the nickel-substituted cobalt ferrite nanoparticles. Furthermore, Fourier-transform infrared spectroscopy results showed that the typical characteristic absorption of the nanoparticles was obtained at wave numbers k = 575 and 374 cm<SUP>−1</SUP>. Finally, the saturation magnetization and coercivity of the nanoparticles increased with the annealing temperature, which is attributed to the increase in magnetic anisotropy constant.