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Articles

RECOVERY GARAM LITHIUM DARI AIR ASIN (BRINE) DENGAN METODA PRESIPITASI Sumarno, Sumarno; Ratnawati, Ratnawati; A. Nugroho, A. Nugroho
TEKNIK Volume 33, Nomor 2, Tahun 2012
Publisher : Fakultas Teknik, Universitas Diponegoro

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Abstract

Lithium demand increases as it is widely used as raw material for rechargeable battery, alloy for airplane, andfuel for fusion nuclear reactor. Lithium is an extremely reactive element, that it is never found as free element innature. Lithium compounds are found in earth crust, with very small concentration (20 – 70 ppm) and totalcontent of more than 20 million tons. The biggest lithium reserve is in seawater (0,14 – 0,25 ppm) andgeothermal water (7 ppm) with total amount of 230 billion tons. There is no industry applies the technology torecover lithium from seawater. Having a vast sea area and abundant geothermal sources, Indonesia needs todevelop a technology to recover lithium from both sources. This research is aimed to recover lithium fromgeothermal water. The experiment was conducted using synthetic and geothermal water with lithiumconcentration range of 220 – 400 ppm, temperature range of 20 – 40°C, and mixing time range of 1 – 4 hours.The experiment was designed with 2 level factorial design. The results show that the most influencing variable ismixing time, while significant interaction amongst variables is not observed. Further experiment usinggeothermal water from Bledug Kuwu with initial lithium concentration of 400 ppm and temperature 30°Cresulted in optimum mixing time, i.e. 3 hours with 92,5% of the lithium could be recovered
VAN DER WAALS MIXING RULES FOR THE REDLICH-KWONG EQUATION OF STATE. APPLICATION FOR SUPERCRITICAL SOLUBILITY MODELING Ratnawati, Ratnawati
REAKTOR Volume 10, Nomor 2, Desember 2006
Publisher : Dept. of Chemical Engineering, Diponegoro University

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Abstract

A solid-supercritical fluid system is highly asymmetric in terms of the size and energy differences of the components. The key point in extending a cubic equation of state to such system is on the choice of proper mixing rules. New mixing rules for the Redlich-Kwong equation of state are developed. The developement is based on the statistical-mechanical theory of the van der Waals mixing rules. The Redlich Kwong equation of state with the proposed mixing rules along with the original ones is used to predict solubilities of solids in supercritical fluid. The prediction is done with kij equal zero, as well as with optimized kij.  The results show superiority of the proposed mixing rules over the original ones. For most of the systems considered, the proposed mixing rules with the kij equal zero are closer to the experimental data than the original ones do. For 28 systems with 521 data points taken from various sources, the original and the proposed mixing rules give the overall AAD of 13.4%, while the original mixing rules give 45.9%.
IMPROVEMENT OF THE REDLICH-KWONG EQUATION OF STATE BY MODIFICATION OF CO-VOLUME PARAMETER Ratnawati, Ratnawati
REAKTOR Volume 13, Nomor 1, Juni 2010
Publisher : Dept. of Chemical Engineering, Diponegoro University

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Abstract

Cubic equations of state are widely used in phase-equilibrium calculations because of their simplicity and accuracy. Most equations of states are not accurate enough for predicting density of liquid and dense gas. A modification on the Redlich-Kwong (RK) equation of state is developed. Parameter b is modified by introducing a new parameter,b, which is a function of molecular weight and temperature. The modification gives a significant improvement over the original RK equation for predicting density. For 6538 data points of 27 compounds, the proposed equation gives only 2.8% of average absolute deviation (AAD), while the original RK and the Soave-Redlich-Kwong (SRK) equations give 11.4% and 11.7%, respectively. The proposed modification improves the performance of the RK equation for predicting vapor pressure as well. For 2829 data points of 94 compounds, the proposed modification lowers the AAD of the RK equation from 1460% down to 30.8%. It is comparable to the famous SRK equation, which give 5.8% of AAD. The advantage of the proposed equation is that it uses only critical pressure and temperature as other equations of states do, and molecular weight, which is easily calculated. Another advantage is that the proposed equation simpler than the SRK equation of state.
NANOTECHNOLOGY AN EMERGING NEW TECHNOLOGY FOR INDONESIA PART I. NANOTECHNOLOGY IN GENERAL Ratnawati, Ratnawati; D.D. Anggoro, anggoro; G.A. Mansoori, G.A. Mansoori
REAKTOR Volume 10 No. 1 Juni 2006
Publisher : Dept. of Chemical Engineering, Diponegoro University

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Abstract

Nanotechnology is shortly defined as the ability to build micro and macro material and product with atomic precistion. Feynman is considered to be the scientist who put a strong foundation for the development of nanotechnology with his phenomenal speech in 1959 entitled "Theres Plenty of Room at the Bottom - An invitation to enter a new field of physics." The invention of scanning tunneling microscope, followed by atomic force microscope, has enabled the world to see atoms and nolecules and opened more possibility for the scientists to develop nanotechnology. Other breakthough in nanotechnology is the discoveries of fullerene, carbon nanotube and diamondoids. Nanotechnology has found various fields of application, such as in biomedical , materials, aerospace, surface science and energy, to name a few, lead by the united States, Europe, and Japan, The technology brings benefits as well as risks to human life. Some of the risks are potentially global in scope. It is why a single, trustworthy, international administration holding controls on the technologyis is urgently needed.
KONVERSI ELEKTROKIMIA AMONIA MENJADI HIDROGEN Ratnawati, Ratnawati; Sumarno, Sumarno; Nugroho, Amin
TEKNIK Volume 31, Nomor 2, Tahun 2010
Publisher : Fakultas Teknik, Universitas Diponegoro

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Abstract

One of the most dangerous pollutants in wastewater is ammonia. The concentration of ammonia inwastewater discharged from nitrogen fertilizer industry is up to 1500 ppm. Ammonia can be removed byseveral methods such as biological denitrification, air-stripping, and ion exchange. The methods cannotreduce the concentration of ammonia to a low level as required for standard quality of wastewater. Theelectrochemical method has recently attracted attention for the treatment of wastewater containing ammonia.This research is aimed to evaluate the effect of ammonia concentration, current density, and time on theelectrolysis process. Synthetic wastewater containing 500-1500 ppm of ammonia was used in this research.The solution was electrolyzed in a electrolytic cell with Pt/SS electrodes. The experiment was conducted byvarying current density in the range of 5 – 10 mA/cm2 and time from 0 to 105 minutes. The experiment resultsshow that as current density rises, the electrolytic reaction occurs more rapidly. On the other hand, initialconcentration of ammonia has negative effect on the final conversion of ammonia.
Prevalence and Clinical Appearance of Obstructive Sleep Apnea (OSA) Among Asthma Patients Astuti, Puji; Yunus, Faisal; Antariksa, Budhi; Ratnawati, Ratnawati
Journal of the Indonesian Medical Association Vol. 61 No. 7 July 2011
Publisher : Journal of the Indonesian Medical Association

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Abstract

Studies on respiratory disorders show decreased sleep quality in asthma patients possibly due to nocturnal asthma symptoms. Recent studies show that OSA is related to bronchial hyperresponsiveness and may be related to asthma. In this observational study, asthma patients who visited Persahabatan Hospital asthma clinic from May 2009 to February 2010 was recruited consecutively. Spirometry and bronchial provocation test (4.5% hyper saline) was performed. OSA was evaluated using Berlin Questionnaire and polysomnography. Anatomical evaluation related to OSA/asthma risk factor or comorbid were performed by one ENT specialist. Diagnosis of OSA was discovered in 20 out of 101 subjects (19.8%) using Berlin questionnaire and 9.8% using polysomnography. The main OSA symptoms found were snoring, fatigue after sleeping, and daytime sleepiness. OSA patient shave higher BMI (28.54kg/m2 vs 21.48kg/m2; p<0.05); larger neck circumference (37.90 cm vs 33.6 cm; p=0.01 OR=2.8 CI=1.28-6.01), decreased FEV1 (56.70% pred vs 59.51% pred). In asthma patients with OSA, 18 (90%) have anatomical upper airway disorder such as septum deviation, sinusitis, adenoid, concha hyperthrophy and long uvula. In conclusion asthma patients have higher prevalence of OSA compared to the general population using both methods. The risk of OSA in asthma are correlated with increased BMI, neck circumference. The main OSA symptom found in asthma patients is snoring. J Indon Med Assoc. 2011;61:273-9.Keywords: Asthma, obstructive sleep apnea, Berlin questionnaire, polysomnography
PENERAPAN TEKNOLOGI FLUIDIZED BED DRYER DENGAN PENAMBAHAN ZEOLIT 3A UNTUK MENINGKATKAN EFISIENSIPENGERINGAN GABAH Hidayati, Noor; P., Utami Diah; Ratnawati, Ratnawati; Suherman, Suherman
JURNAL TEKNOLOGI KIMIA DAN INDUSTRI Volume 2, Nomor 4, Tahun 2013
Publisher : JURNAL TEKNOLOGI KIMIA DAN INDUSTRI

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Abstract

Now, drying paddy  using conventional method is irrelevant to used. The need of grain increasing each year is one of the main factor that pushes scientist to invent new methods of drying paddy grain. The old method is unusefull since it takes up space, needed the sun as the drying media which causes a long drying time. One of the alternative of drying paddy grain is by using mechanic dryer. By using this type of dryer, the process of drying takes faster comparing to the old method and the distribution of grain is supplied continuously. The dryer which uses fluidized bed  can be one of the solution due to its less energy consumption, a better drying result and high drying capacity. The variable used to identify drying performance is temperature and loading weight. From the experiment, it is resulted that the best temperature for drying paddy grain is 50 C with the flowrate 3,5 m/s.
PERAN LABA MEMODERASI HUBUNGAN MODAL KERJA DAN BIAYA EKUITAS (Studi Kasus pada Perusahaan Manufaktur di Bursa Efek Indonesia) Ratnawati, Ratnawati
Students Journal of Economic and Management Vol 1, No 1 (2012): VOL. 1 NO. 1 EDISI PERTAMA 2012
Publisher : Students Journal of Economic and Management

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Abstract

This study aimed to examine the effect of Nibe to Working Capital Gain and equity costs of case studies on the effects of manufacturing companies on Bursa Efek  Indonesia (BEI). The samples used in this research is a group of companies manufacturing the category of companies whose shares are actively traded on the Stock Exchange always during peeode observations (2007-2010). The number of samples obtained by category amounted to 19 companies over a period of 4 years. Secondary data was obtained from the Indonesia Stock excange (IDX) annual statistics for the period 2007 to 2010. The analysis used in this study is multiple regression techniques (multiple regression) to test the hypothesis t-test and F-test at the 5% level of significance (α = 0.05). Hypothesis test results indicate that the variable income and variable working capital Nibe together equally significant effect on the cost of equity. This result indicates that these two variables are jointly able to significantly influence the cost of equity. The test results also found that working capital and cost of equity has a negative and significant effect, because it has the value of the Standardized Beta Coefficiens 0000 0601 and its significance is greater than alpha (0.05). Keywords: Nibe earnings, working capital, cost of equity
STUDI ANALISIS VARIANS RANKING DUA- ARAH FRIEDMAN TERHADAP KOMPETENSI DIMENSI PENGETAHUAN AUDITOR DI KANTOR AKUNTAN PUBLIK JAKARTA Ratnawati, Ratnawati; Samosir, Perak
MAJALAH ILMIAH WIDYA 2012
Publisher : MAJALAH ILMIAH WIDYA

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Abstract

In conducting the auditing, the auditor should have the competence dimension of knowledge. It can be analyzed through therespondents answers to the statements relating to the competence dimension of knowledge of an auditor. The purpose of this studyis to see if there is a statement to the effect of the respondents answer and whether there is a correlation between the grain statements.The method used analysis of auditor competence dimension of knowledge in performing auditing and other data collected byquestinaires distributed to 30 Public Auditor offices in Jakarta. The result showed that no significant differences from respondentsanswers to the statement items relating to the auditor’s competence of knowledge dimension
DEVELOPING THEMATIC ENGLISH MULTIMEDIA FOR TEACHING VOCABULARY TO YOUNG LEARNERS Ratnawati, Ratnawati
Language Circle: Journal of Language and Literature Vol 9, No 1 (2014): October 2014
Publisher : Faculty of Languages ​​and Arts, State University of Semarang

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Abstract

The observed inappropriateness comes from textbooks used in teaching young learners are too difficult, dominated by written form, unspecific, and decontextualized interactive multimedia. Hence, the researcher would like to develop Thematic English Multimedia (TEM) for teaching vocabulary to young learnersat kindergarten B of Islamic Centre Purwodadi, Grobogan. This study employed R&D Design proposed by Borg and Gall (2003:772). Seven stages employed were information and research collecting, planning, developing, validating, revising, try out, and producing final TEM. Observation, interview, validation, performance-based assessment, and pre also post-test were administered to collect data. From results of collected data, they were found that applying TEM got positive perspectives toward teaching and learning process. In line with above statements, TEM is effective and feasible to teach young learners at kindergarten B of Islamic Centre Purwodadi, Grobogan.
Co-Authors A. Nugroho A. Nugroho A. Yoshi, Linda AGUS PURWANTO Aji Prasetyaningrum Amin Nugroho Andinawati, Mia Andri Cahyo Kumoro anggoro D.D. Anggoro, anggoro Ansyari Mone, Ansyari Anwar, Asni Aprilina Purbasari Ari Pani Desvina Arsawaty Arsawaty, Arsawaty Aryadi Suwono Batau, Haliah Budhi Antariksa Budiwati Budiwati Catarina Sri Budiyati Chifdillah, Nino Adib Decy Lukitasari Diah Susetyo Retnowati Didih Faridah, Didih Dyah Hesti Wardhani Enda Puspitasari Etika Rachmawati, Etika Faisal Yunus Fitria Fitria G.A. Mansoori G.A. Mansoori, G.A. Mansoori Hartati Tamti, Hartati Hartono, Damin Henry, R L Inderiati, Sitti - Iyus Hendrawan Johannes Leonard K., Zaenal Kunda, Asri Kusumaningtyas, Dyah Arum L. Buchori Lilies Youlia Friatin, Lilies Youlia Linda Aliffia Yoshi, Linda Aliffia M. A. Graciafernandy M. Zen Rahfiludin Mappamiring Mappamiring Martha Irene Kartasurya Massiseng, Andi Nur Apung Mohamad Djaeni Morton, J Muhajirin Muhajirin Mulyadi, Deny Muhamad nanang nanang Nguyen, V Noor Hidayati Nugraha, Cahyarani Daulika NURLIANA NURLIANA Perak Samosir Puji Astuti Pujiati, Tri Rahma Ayu Maharani Ramdhani, Eka Chandra Razali Razali Reski Praminasari, Reski Rohayati Arifin, Rohayati Rokhman, M.Taufiq Noor Salim, Amir Samudro, H.M Septiani, Hemas Septiani, Mimin Setyorini Setyorini Silalahi, Oberlin Since, Since Singgih Hartanto Slamet Slamet Sugeng, Purwito Suhandoyo Suhandoyo, Suhandoyo Suherman Suherman Sulastri Sulastri Sumarno Sumarno Suratsih Suratsih Suryani Yuliyanti, Suryani Suseno, Purbo Tavip Dwi Wahyuni, Tavip Dwi Thomas, P S Tiala, Fabia Utami Diah P. Utami, Kurniati Dwi Wibawa, Surya Aji Y., Andri Yenny Widianty, Yenny Yustina Linasari Zulkifli N