Investigations on thermodynamic processes of a novel pneumatic drive asymmetric Gifford-McMahon cycle cryorefrigerator

In this paper, a numerical and experimental investigation is conducted on a novel pneumatic-drive asymmetric Gifford-McMahon cycle cryorefrigerator for the first time. In the pneumatic-drive asymmetric Gifford-McMahon cycle cryorefrigerator, the duration of the assistance space exhaust process is kept higher than that of the assistance space intake process. Therefore, the displacer moves faster at the lower dead centre and slower at the upper dead centre inside the expander cylinder, which makes the duration of expansion process longer. The numerical model solves the governing equations of the refrigerant and dynamics of free-floating displacer iteratively to illustrate the refrigeration mechanisms. Additionally, the model computes the performance parameters of the cryorefrigerator, like refrigerating capacity, and specific refrigerating capacity. By adopting the numerical model, the impact of the loitering time on the thermodynamic processes is elaborated. It is perceived that, both refrigerating capacity and specific refrigerating capacity reduces with an increase in the loitering time. The experimental cooling characteristics are studied for different values of discharge to suction pressure ratios of helium compressor.

Examining Small-Town Growth and Expansion in Peri-urban Areas of Small Cities: Evidence from Peripheries of Three Small Cities in Central Java

Urbanization in small and medium-sized cities in Java is marked by an urban expansion process to the surrounding areas, forming the growing small towns in their peripheries. Using the case of the extended urban areas of Tegal, Pekalongan and Magelang in Central Java, this study examined small-town growth and development in peri-urban areas of small and medium cities. It first looked at the growth of small towns in the peri-urban areas of these small cities and then identified various factors and mechanisms that contribute to the formation, growth and expansion of small towns. The study further looked into the challenges and implications of the trend toward policies for managing such processes more sustainably. The growth of urbanized villages in some kabupatens (non-urban districts or regencies) surrounding these small cities, as documented by the national statistical board from 1990 to 2017, was used as the basis for analyzing these factors. This paper concludes with a discussion on the challenges and policy implications for growing small towns. The findings of this study can be useful for formulating a better approach to managing urbanization processes in the future. Abstrak. Urbanisasi kota-kota kecil dan menengah di Jawa ditandai dengan proses perluasan kota ke wilayah sekitarnya, membentuk kota-kota kecil yang berkembang di pinggirannya. Dengan menggunakan kasus perluasan wilayah Tegal, Pekalongan dan Magelang di Jawa Tengah, penelitian ini mengkaji pertumbuhan dan perkembangan kota kecil di wilayah pinggiran kota kecil dan menengah. Ini pertama-tama melihat pertumbuhan kota-kota kecil di daerah pinggiran kota-kota kecil ini dan kemudian mengidentifikasi berbagai faktor dan mekanisme yang berkontribusi pada pembentukan, pertumbuhan, dan perluasan kota-kota kecil. Studi ini lebih jauh melihat tantangan dan implikasi dari tren terhadap kebijakan untuk mengelola proses tersebut secara lebih berkelanjutan. Pertumbuhan desa urban di beberapa kabupaten (kabupaten atau kabupaten non-urban) di sekitar kota-kota kecil tersebut, sebagaimana didokumentasikan oleh BPS (Badan Pusat Statistik) dari tahun 1990 hingga 2017, digunakan sebagai dasar untuk menganalisis faktor-faktor tersebut. Makalah ini diakhiri dengan diskusi tentang tantangan dan implikasi kebijakan untuk pertumbuhan kota-kota kecil. Temuan studi ini dapat berguna untuk merumuskan pendekatan yang lebih baik untuk mengelola proses urbanisasi di masa depan. Kata kunci. Jawa Tengah, kota kecil, urbanisasi, ekspansi kota.

Study on the Hydro-Thermal-Mechanical Characteristics of the Lime-Soil Compaction Pile in the Forming Process

To study the effect of the lime-soil compaction pile on the collapsible loess foundation and the influence of water-heat-force characteristics on the soil during compaction, the field test of lime-soil compaction pile treatment of collapsible loess foundation is carried out. This paper monitors the process of soil temperature, water, and soil pressure change in the process of pile forming. According to the macroprocess and micromechanism of lime-soil compaction pile treatment of collapsible loess foundation, the qualitative law of water-heat-force change in the process of pile forming is obtained. Meanwhile, the influence of soil damage is introduced in the process of compaction expansion. The model of pore expansion under linear damage conditions in the plastic zone is established. The formula of radial stress distribution under damage conditions is given. The influence of different damage factors on the expansion process is analyzed.

Algorithms for Finding Diameter Cycles of Biconnected Graphs

In this paper, we first coin a new graph theoretic problem called the diameter cycle problem with numerous applications. A longest cycle in a graph G = (V, E) is referred to as a diameter cycle of G iff the distance in G of every vertex on the cycle to the rest of the on-cycle vertices is maximal. We then present two algorithms for finding a diameter cycle of a biconnected graph. The first algorithm is an abstract intuitive algorithm that utilizes a brute-force mechanism for expanding an initial cycle by repeatedly replacing paths on the cycle with longer paths. The second algorithm is a concrete algorithm that uses fundamental cycles in the expansion process and has the time and space complexity of O(n^6) and O(n^2), respectively. To the best of our knowledge, this problem was neither defined nor addressed in the literature. The diameter cycle problem distinguishes itself from other cycle finding problems by identifying cycles that are maximally long while maximizing the distances between vertices in the cycle. Existing cycle finding algorithms such as fundamental and longest cycle algorithms do not discover cycles where the distances between vertices are maximized while also maximizing the length of the cycle.