Brownian dynamics of rigid particles in an incompressible fluctuating fluid by a meshfree method

A meshfree Lagrangian method for the fluctuating hydrodynamic equations (FHEs) with fluid-structure interactions is presented. Brownian motion of the particle is investigated by direct numerical simulation of the fluctuating hydrodynamic equations. In this framework a bidirectional coupling has been introduced between the fluctuating fluid and the solid object. The force governing the motion of the solid object is solely due to the surrounding fluid particles. Since a meshfree formulation is used, the method can be extended to many real applications involving complex fluid flows. A three-dimensional implementation is presented. In particular, we observe the short and long-time behaviour of the velocity autocorrelation function (VACF) of Brownian particles and compare it with the analytical expression. Moreover, the Stokes-Einstein relation is reproduced to ensure the correct long-time behaviour of Brownian dynamics.Comment: 24 pages, 2 figure

FAKTOR RISIKO LINGKUNGAN PADA KEJADIAN PENYAKIT ASMA DI WILAYAH KERJA PUSKESMAS MANGKANG KOTA SEMARANG

Asma di Kota Semarang mengalami kenaikan jumlah dari tahun 2013 berjumlah 5040 kasus menjadi 5711 kasus pada tahun 2014. Prevalensi penyakit asma di Puskesmas Mangkang Kota Semarang sebesar 1,5% dengan jumlah kasus tahun 2014 dan 2015 sebanyak 117 dan 133 kasus. Selain adanya riwayat asma dalam keluarga, adanya partikulat pencemar udara juga berkontribusi terhadap timbulnya asma. Jenis partikulat diantaranya PM10 dan PM2,5. Partikulat pencemar udara di dalam rumah juga dipengaruhi kondisi fisik rumah. Penelitian ini bertujuan untuk mengetahui hubungan faktor risiko lingkungan dengan kejadian asma di wilayah kerja Puskesmas Mangkang Kota Semarang. Penelitian ini menggunakan jenis penelitian analitik observasional dengan desain penelitian case control. Besar sampel pada masing masing kelompok kasus dan kontrol sama yaitu 37 responden. Sampel pada kelompok kasus merupakan pasien yang didiagnosis menderita asma yang berobat di Puskesmas Mangkang Kota Semarang pada bulan November 2015-April 2016. Analisis data menggunakan analisis univariat dan bivariat dengan uji Chi Square. Rata rata suhu udara adalah 31 derajat Celcius, kelembaban udara 65%, dan konsentrasi PM10 585µg/m3. Hasil penelitian menunjukkan dari 8 variabel bebas yang diteliti terdapat 2 variabel yang berhubungan dengan kejadian asma yaitu kelembaban udara dalam rumah (p-value= 0,048; OR= 3,96; 95% CI= 1,140-13,756) dan keberadaan hewan peliharaan berbulu (p-value= 0,036; OR= 2,70; 95% CI= 1,056-6,941). Kesimpulan dari penelitian ini faktor risiko yang berhubungan dengan kejadian asma di Wilayah Kerja Puskesmas Mangkang Kota Semarang adalah kelembaban udara dalam rumah dan keberadaan hewan peliharaan. Kata Kunci: Asma, PM10, Pencemaran Udara, Semaran

Social Network Based Substance Abuse Prevention via Network Modification (A Preliminary Study)

Substance use and abuse is a significant public health problem in the United States. Group-based intervention programs offer a promising means of preventing and reducing substance abuse. While effective, unfortunately, inappropriate intervention groups can result in an increase in deviant behaviors among participants, a process known as deviancy training. This paper investigates the problem of optimizing the social influence related to the deviant behavior via careful construction of the intervention groups. We propose a Mixed Integer Optimization formulation that decides on the intervention groups, captures the impact of the groups on the structure of the social network, and models the impact of these changes on behavior propagation. In addition, we propose a scalable hybrid meta-heuristic algorithm that combines Mixed Integer Programming and Large Neighborhood Search to find near-optimal network partitions. Our algorithm is packaged in the form of GUIDE, an AI-based decision aid that recommends intervention groups. Being the first quantitative decision aid of this kind, GUIDE is able to assist practitioners, in particular social workers, in three key areas: (a) GUIDE proposes near-optimal solutions that are shown, via extensive simulations, to significantly improve over the traditional qualitative practices for forming intervention groups; (b) GUIDE is able to identify circumstances when an intervention will lead to deviancy training, thus saving time, money, and effort; (c) GUIDE can evaluate current strategies of group formation and discard strategies that will lead to deviancy training. In developing GUIDE, we are primarily interested in substance use interventions among homeless youth as a high risk and vulnerable population. GUIDE is developed in collaboration with Urban Peak, a homeless-youth serving organization in Denver, CO, and is under preparation for deployment