Optimization of Dimples in Microchannel Heat Sink with Impinging Jets—Part B: the Influences of Dimple Height and Arrangement

The combination of a microchannel heat sink with impinging jets and dimples (MHSIJD) can effectively improve the flow and heat transfer performance on the cooling surface of electronic devices with very high heat fluxes. Based on the previous work by analysing the effect of dimple radius on the overall performance of MHSIJD, the effects of dimple height and arrangement were numerically analysed. The velocity distribution, pressure drop, and thermal performance of MHSIJD under various dimple heights and arrangements were presented. The results showed that: MHSIJD with higher dimples had better overall performance with dimple radius being fixed; creating a mismatch between the impinging hole and dimple can solve the issue caused by the drift phenomenon; the mismatch between the impinging hole and dimple did not exhibit better overall performance than a well-matched design

Quantum-defect theory of resonant charge exchange

We apply the quantum-defect theory for $-1/R^4$ potential to study the resonant charge exchange process. We show that by taking advantage of the partial-wave-insensitive nature of the formulation, resonant charge exchange of the type of $^1$S+$^2$S can be accurately described over a wide range of energies using only three parameters, such as the \textit{gerade} and the \textit{ungerade} $s$ wave scattering lengths, and the atomic polarizability, even at energies where many partial waves contribute to the cross sections. The parameters can be determined experimentally, without having to rely on accurate potential energy surfaces, of which few exist for ion-atom systems. The theory further relates ultracold interactions to interactions at much higher temperatures.Comment: 8 pages, 7 figure

N(HI) and jet power/emission in AGNs

Neutral hydrogen (HI) 21 cm absorption has been detected against more and more powerful radio jets. In this work, based on the Guppta et al. 2006a sample, we present our preliminary study of the correlations between the HI column density N(HI) and the jet power, N(HI) versus the low frequency luminosity at 408MHz, and N(HI) versus the radio luminosity at 1400MHz.Comment: 3 pages, 1 figures, Multiwavelength Variability of Blazars Guangzhou, China, Sept. 22-24, 2010; will be published by JA

Studi Alternatif Analisis Sambungan Balok-kolom Dengan Sistem Pracetak Pada Gedung Volendam Holland Park Condotel Kota Batu

Sebagai kota wisata, Kota Batu dituntut dengan maraknya pembangunan Condotel di dekat tempat-tempat wisata. Akan tetapi dengan banyaknya gedung – gedung yang dibangun membuat lahan yang tersedia semakin lama semakin sempit. Oleh karena itu, Kota Batu mulai membangun gedung–gedung bertingkat untuk mengatasi kekurangan lahan yang semakin sempit. Pembangunan gedung bertingkat saat ini sebagian besar masih tetap menggunakan metode beton bertulang konvensional dengan menggunakan bekisting yang dicor di tempat yang akan menelan biaya lebih mahal karena membutuhkan banyak sekali bekisting serta akan memakan waktu yang lebih lama. Akan tetapi sekarang ada terobosan baru untuk mengurangi penggunaan bekisting yang banyak dan mengurasi lamanya durasi pengerjaan, yaitu dengan menggunakan metode pracetak yang dibuat di pabrik atau di lokasi proyek kemudian dirakit. Konsep pembangunan mengacu ke dalam SNI 03- 1726-2012 tentang tata cara perencanaan ketahanan gempa untuk struktur bangunan gedung dan non gedung serta SNI 03-2847-2002 tentang tata cara perhitungan struktur beton sehingga acuan kedua peraturan tersebut akan didapatkan struktur yang tahan gempa, efektif, dan efisien. Dalam studi ini merupakan analisis Gedung Volendam Holland Park Condotel Kota Batu dengan zona gempa 4 yang di rencanakan kembali dengan menggunakan metode pracetak

Variability of Contact Process in Complex Networks

We study numerically how the structures of distinct networks influence the epidemic dynamics in contact process. We first find that the variability difference between homogeneous and heterogeneous networks is very narrow, although the heterogeneous structures can induce the lighter prevalence. Contrary to non-community networks, strong community structures can cause the secondary outbreak of prevalence and two peaks of variability appeared. Especially in the local community, the extraordinarily large variability in early stage of the outbreak makes the prediction of epidemic spreading hard. Importantly, the bridgeness plays a significant role in the predictability, meaning the further distance of the initial seed to the bridgeness, the less accurate the predictability is. Also, we investigate the effect of different disease reaction mechanisms on variability, and find that the different reaction mechanisms will result in the distinct variabilities at the end of epidemic spreading.Comment: 6 pages, 4 figure

Damping in 2D and 3D dilute Bose gases

Damping in 2D and 3D dilute gases is investigated using both the hydrodynamical approach and the Hartree-Fock-Bogoliubov (HFB) approximation . We found that the both methods are good for the Beliaev damping at zero temperature and Landau damping at very low temperature, however, at high temperature, the hydrodynamical approach overestimates the Landau damping and the HFB gives a better approximation. This result shows that the comparison of the theoretical calculation using the hydrodynamical approach and the experimental data for high temperature done by Vincent Liu (PRL {\bf21} 4056 (1997)) is not proper. For two-dimensional systems, we show that the Beliaev damping rate is proportional to $k^3$ and the Landau damping rate is proportional to $T^2$ for low temperature and to $T$ for high temperature. We also show that in two dimensions the hydrodynamical approach gives the same result for zero temperature and for low temperature as HFB, but overestimates the Landau damping for high temperature.Comment: 11 pages, 4 figure

Exact solution of mean geodesic distance for Vicsek fractals

The Vicsek fractals are one of the most interesting classes of fractals and the study of their structural properties is important. In this paper, the exact formula for the mean geodesic distance of Vicsek fractals is found. The quantity is computed precisely through the recurrence relations derived from the self-similar structure of the fractals considered. The obtained exact solution exhibits that the mean geodesic distance approximately increases as an exponential function of the number of nodes, with the exponent equal to the reciprocal of the fractal dimension. The closed-form solution is confirmed by extensive numerical calculations.Comment: 4 pages, 3 figure

Peering from the outside in: viscoelastic properties of the extracellular matrix dictate spatial organization and apoptosis resistance in mammary epithelial cells

The compliance of the extracellular matrix (ECM) differs between tissues and is altered in tumors. We examined the consequence of modifying the viscoelastic properties of the ECM on mammary epithelial cell (MEC) morphogenesis and apoptosis regulation. Results showed that the elastic modulus of the ECM exerts a profound effect on MEC tissue organization and gene expression that correlates with changes in actin organization and apoptosis resistance. Altering the rigidity of the ECM directly influences integrin expression and additionally modifies integrin-induced gene expression in association with actin reorganization. These data suggest that the compliance of the ECM may cooperatively regulate cell behavior by altering integrin function. Studies are now underway to investigate the possibility that these effects are mediated via changes in integrin-actin cytoskeletal dynamics

Perencanaan Alternatif Struktur Castellated Beam Non Komposit Gedung Volendam Holland Park Condotel Kota Batu

Remaja ini pembangunan di Indonesia berkembang sangat pesat. Kemajuan pembangunan yang sangat pesat ini menyebabkan area bebas semakin sedikit dan sempit. Maka, daerah daerah maju maupun berkembang mulai membangun gedung gedung bertingkat untuk mengatasi kebatasan lahan. Sebagian besar daerah daerah di Indonesia masih banyak yang menggunakan bangunan gedung yang menggunakan beton bertulang yang relative membutuhkan waktu lama dalam pembangunannya dan memiliki keterbatasan dalam gedung berbentang panjang dan membutuhkan jarak antar kolom yang relatif berbentang pendek. Untuk itu perlu bahan lain yang dapat mengatasi permasalahan tersebut, bahan tersebut ialah baja, karena baja merupakan produk pabrik dan pemasangannya mudah sehingga dapat mempersingkat waktu pengerjaan bangunan struktur. Dan baja merupakan bahan yang sangat cocok untuk bangunan berbentang panjang sehingga dapat mengurangi jumlah kolom pada bangunan tersebut, dan pada studi ini menggunakan perencanaan baja Castellated beam yang mampu menahan tegangan lebih kuat dari baja biasa karena tingginya mencapai 1,5 kali lebih tinggi dari baja biasa dan lubang lubang yang terdapat pada baja castellated beam dapat di gunakan untuk jalan lewat pipa pipa saluran pada gedung tersebut sehingga dapat menghemat penggunaan area dan tidak akan mengurangi tinggi plafon yang biasanya berkurang karena di lewat pipa pipa. Pembangunan ini mengacu pada SNI 03 1726 2002 sehingga dengan mengacu pada peraturan itu menghasilkan bangunan gedung yang efisien, efektif dan tahan gempa. Dalam analisis berikut merupakan penelitian dari gedung Vollendam di Holland Park Condotel kota batu. Dengan Zona gempa 4 yang menggunakan perencanaan Baja Castellated Beam. Dari analisis ini di simpulkan bahwa baja yang digunakan untuk balok memiliki dimensi 250x250x8x13mm dan untuk kolom memiliki dimensi 622x357x26x15mm. dan terbukti aman untuk bangunan ini karena memenuhi syarat perhitungan momen Φ Mn ≥ Mu dan perhitungan geser Φ Vn ≥ Vu

Transient radial flow to a well in an unconfined aquifer. Part 1, An evaluation of some conceptual methods

The analytic solutions of Boulton (1954) and Neuman (1972) for transient flow to a well in an unconfined aquifer are based on the assumption that the role of the unsaturated zone can be adequately accounted for by restricting attention to the release of water from the zone through which the water table moves. Both researchers mathematically treat this released water as a time-dependent source term. The differences between the models of Boulton and Neuman are that the former neglects vertical components of flow in the aquifer, but allows for an exponential process for the release of water as a function of time, whereas the latter assumes instantaneous release from storage, but accounts for vertical components of flow. Given this set of assumptions, we examine the applicability of these two methods using a general purpose numerical model through a process of verification extension and comparison. The issues addressed include: the role of well-bore storage in masking intermediate-time behavior, combined effects of exponential release as well as vertical flow, logic for vertical averaging of drawdowns, and the sensitivity of system response to the magnitude of specific yield. The issue of how good the assumptions of Boulton and Neuman are in the context of the general theory of unsaturated flow is addressed in part 2 of this two-part series of reports