Academic literature on the topic 'Parametro di densità'
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Journal articles on the topic "Parametro di densità"
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Bernardi, L. "La risonanza magnetica nella patologia maxillo-facciale." Rivista di Neuroradiologia 4, no. 3_suppl (December 1991): 141–46. http://dx.doi.org/10.1177/19714009910040s325.
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La RM ha avuto un forte impatto nella diagnosi, nel trattamento e nel follow-up (post-chirurgico, post-radioterapico) delle neoplasie del massiccio facciale. Infatti mentre l'aspetto delle strutture anatomiche alla TC, anche con mdc, dipende da un solo parametro fisico, la densità, l'intensità di segnale dei tessuti alla RM dipende da almeno quattro caratteristiche fisiche: i tempi di rilassamento T1 e T2, la densità protonica ed il flusso. La superiore risoluzione di contrasto della RM rispetto alla TC deriva dalla sua capacità di individuare ed evidenziare queste varie proprietà fisiche. La capacità multiplanare della RM è particolarmente vantaggiosa nel massiccio facciale. La RM permette inoltre la diretta visualizzazione, senza l'uso di mdc, di strutture vasali ed è quindi in grado di dimostrare l'aumentata vascolarizzazione tumorale. La maggiore deficienza diagnostica della RM nel massiccio facciale è la sua insufficienza nell'evidenziare le calcificazioni e le sottili alterazioni ossee (erosione, iperostosi). Per quanto concerne la tecnica, le sequenze T1 pesate, a causa del loro alto rapporto segnale-rumore, sono le migliori per lo studio dell'anatomia ed evidenziano in modo ottimale l'interfaccia tumore-grasso. Le sequenze T2 pesate invece sono le più adatte per evidenziare l'interfaccia tumore-muscolo. Le sequenze DP rappresentano una combinazione di informazioni T1 e T2 pesate.
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Andreula, C. F. "Il mezzo di contrasto per via venosa nello studio TC dell'encefalo." Rivista di Neuroradiologia 1, no. 2 (August 1988): 169–80. http://dx.doi.org/10.1177/197140098800100208.
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L'uso del mezzo di contrasto per via venosa nella TC dell'encefalo svolge un ruolo chiave nell'incremento di sensibilità della metodica, ma vieppiù immette altri dati nel raggiungimento di una diagnosi di specificità. L'autore riporta e discute le concentrazioni, le dosi riguardanti il mezzo di contrasto, sottolineando la necessità di uso di mezzi di contrasto a bassa osmolarità per la minore incidenza di effetti indesiderati, con predilezione per i non ionici. Le tecniche di somministrazione più utilizzate sono la bifasica la metodica del bolo rapido e le tecniche speciali con doppia dose di contrasto e scansioni ritardate. I reperti TC sono stati distinti utilizzando come parametro di valutazione la barriera ematoencefalica, importante struttura anatomo funzionale, la cui integrità, assenza, danneggiamento o malfunzionamento determinano rilievi tomodensitometrici di contrast-enhancement (CE) importanti per una diagnosi di specificità. L'autore inoltre sottolinea l'importanza della valutazione della dinamica del CE e delle curve densità/tempo, utilizzando la tecnica speciale di doppia dose e scansioni ritardate, discutendone i rapporti con le sequenze di impulsi in Risonanza Magnetica.
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Lorusso, V., and E. P. Tirone. "Mezzi di contrasto paramagnetici." Rivista di Neuroradiologia 1, no. 2 (August 1988): 207–12. http://dx.doi.org/10.1177/197140098800100214.
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Vengono descritti i parametri che influenzano l'intensità del segnale nella RMN ad immagini. I tempi di rilassamento T1 e T2 e la densità protonica vengono descritti come parametri tissutali e vengono esaminate le possibiltà di influenzare tali parametri mediante ioni, complessi e gas paramagnetici.
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Syafiya, Auladina, and Suwarno Hadisusanto. "KOMUNITAS MAKROZOOBENTOS DI KAWASAN PENAMBANGAN PASIR DI SUNGAI PROGO (Macrozoobenthos Community in Sand Mining Area of Progo River)." Jurnal Manusia dan Lingkungan 26, no. 2 (October 8, 2020): 52. http://dx.doi.org/10.22146/jml.40255.
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AbstrakSungai memiliki peranan penting bagi manusia dan makhluk hidup lainnya, di antaranya adalah sebagai habitat bagi komunitas makrozoobentos dan pemanfaatan material berupa pasir dan batu sebagai bahan bangunan. Sungai Progo merupakan salah satu sungai yang hampir di sepanjang sungainya terdapat aktivitas penambangan pasir. Jika aktivitas ini dilakukan terus menerus dalam jumlah banyak dan tanpa pengawasan yang baik dapat menyebabkan terjadinya erosi dan degradasi serta sedimentasi pada bagian-bagian tertentu sungai. Maka dari itu dilakukan penelitian ini untuk mempelajari pengaruh aktivitas penambangan pasir terhadap distribusi dan kemelimpahan komunitas makrozoobentos di Sungai Progo, serta Functional Feeding Group (FFG) yang paling melimpah dan parameter fisiko-kimia yang memengaruhinya. Penelitian ini dilakukan dalam tiga tahap, yaitu mencuplik dan preparasi sampel makrozoobentos, identifikasi sampel, dan pengukuran parameter fisiko-kimia. Aktivitas penambangan pasir di Sungai Progo berpengaruh secara tidak langsung terhadap makrozoobentos, yaitu dengan menyebabkan adanya erosi dan degradasi di kawasan penambangan pasir serta sedimentasi di bagian hilir. FFG makrozoobentos di Sungai Progo yang paling melimpah adalah tipe scraper dan collector. Berdasarkan analisis regresi dan korelasi Pearson didapatkan hasil bahwa fosfat berkorelasi positif terhadap densitas makrozoobentos di bagian hulu Sungai Progo, intensitas cahaya berkorelasi positif terhadap densitas makrozoobentos di bagian tengah Sungai Progo, dan kecepatan arus berkorelasi positif terhadap densitas makrozoobentos di bagian hilir Sungai Progo. AbstractRiver has an important role for human and other organisms, among them are as habitat of macrozoobenthos community and the utilization of the material, such as river sand and gravel for building material. Progo River is one of rivers which have sand mining activities almost all along the river. If this activity being done continuously, in a big amount and without a good supervision, it could lead to erosion, degradation and sedimentation in some specific parts. Therefore, this research has an aim to study the effects of sand mining activity towards the distribution and the abundance of macrozoobenthos community in Progo River, and also to study which Functional Feeding Group (FFG) is the most abundant and the physic-chimic parameter that affecting them. This research was conducted in three steps, sampling and preparation of macrozoobenthos’s sample, sample’s identification, and the measurement physicochemical parameter. Sand mining activity in Progo River effect indirectly towards macrozoobenthos by causing erosion and degradation in sand mining area as well as sedimentation in downstream. The most abundant FFG of macrozobenthos in sand mining area of Progo River are scraper and collector. Based on regression and Pearson correlation analysis the results show that phosphate correlated positively against the density of macrozoobenthos in the headwaters of Progo River, light intensity correlated positively against the density of macrozoobenthos in the midstream of the Progo River, and current velocity correlated positively against the density of macrozoobenthos in the downstream of the Progo River.
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., Jamaluddin, Septian Tri Nugraha, Maria Maria, and Emi Prasetyawati Umar. "PREDIKSI TOTAL ORGANIC CARBON (TOC) MENGGUNAKAN REGRESI MULTILINEAR DENGAN PENDEKATAN DATA WELL LOG." JURNAL GEOCELEBES 2, no. 1 (April 17, 2018): 1. http://dx.doi.org/10.20956/geocelebes.v2i1.3568.
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Penelitian ini bertujuan untuk menentukan potensi batuan induk di Formasi Talangakar dengan melihat parameter total organik carbon (TOC). TOC dimodelkan dengan melakukan crossplot antara TOC measured dengan log gamma ray, log densitas, log neutron-porosity, log resistivity, dan log P wave (multi linier regresi). Formasi Talangakar yang menjadi target pada studi ini terletak pada kedalaman 2280 m-2885 m, memiliki material organik yang kaya dengan TOC berkisar antara 1.09 %-1.29 %. Pemodelan TOC didapatkan regresi sebesar 0.1432 terhadap parameter log (log gamma ray, log density, log Neutron-Porosity, log Sonik, dan log Resistivity).
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Ismail, Mochamad Furqon Azis, and Ankiq Taofiqurohman. "Sebaran Spasial Suhu, Salinitas dan Densitas di Perairan Kepulauan Sangihe Talaud Sulawesi Utara." Jurnal Kelautan Tropis 23, no. 2 (April 14, 2020): 191–98. http://dx.doi.org/10.14710/jkt.v23i2.7290.
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The Sangihe Talaud waters are part of the toll road of the Indonesian Throughflow, which has an important role in the transport of seawater properties from the Pacific Ocean to the Indian Ocean. To understand the distribution pattern of physical oceanography parameters namely temperature, salinity, density around the waters of Sangihe Talaud, the research expedition Widya Nusantara Expedition (EWIN) has been conducted using the research vessel Baruna Jaya VIII. The temperature, salinity, and density of the seawater were measured using the CTD Seabird 911plus instrument at 33 stations distributed on the Sangihe Talaud waters. The results of the temperature analysis showed the presence of surface temperature zoning between the Sulawesi Sea and the north of the Maluku Sea, while the salinity distribution showed a low to high salinity gradient from the east to the west side of the Sangihe Talaud waters. The density distribution represents three zones of surface density detected in the north of the Maluku Sea, the northeast side and the west side of the Sangihe and Talaud waters. Perairan kepulauan Sangihe Talaud merupakan bagian dari jalur tol laut Arus Lintas Indonesia yang memiliki peran penting dalam transpor properti air laut dari Samudera Pasifik ke Samudera Hindia. Untuk mengungkap pola sebaran parameter oseanografi fisik seperti suhu, salinitas dan densitas laut di perairan kepulauan Sangihe Talaud, telah dilakukan kegiatan penelitian Ekspedisi Widya Nusantara (EWIN) dengan menggunakan kapal riset Baruna Jaya VIII. Suhu, salinitas, dan densitas air laut diukur dengan menggunakan instrumen CTD Seabird 911Plus pada 33 stasiun pengamatan yang tersebar di perairan Kepulauan Sangihe Talaud. Hasil Analisa suhu menunjukan adanya zonasi sebaran suhu permukaan antara laut Sulawesi dan utara Laut Maluku, adapun sebaran salinitas menunjukan adanya gradien salinitas rendah ke tinggi dari sisi timur ke sisi barat perairan kepulauan Sangihe Talaud. Sedangkan sebaran densitas laut memperlihatkan adanya tiga zonasi densitas permukaan yang terdeteksi di utara Laut Maluku, sisi timur laut dan sisi barat perairan kepulauan Sangihe Talaud.
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Rachman, Arief. "Struktur Komunitas Fitoplankton di Area Tambang Timah dan Perairan Sekitar Kabupaten Bangka Barat." Jurnal Teknologi Lingkungan 20, no. 2 (July 31, 2019): 189. http://dx.doi.org/10.29122/jtl.v20i2.2938.
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ABSTRACTTin mining in the coastal waters of West Bangka Regency is known to affect water quality, which has an impact on the phytoplankton community structure. This research aims to study phytoplankton communities in mining tin areas and outside of mining areas (non-mining areas). Sampling was carried out in 22 sampling stations with 7 stations in the tin mining area. Phytoplankton samples were taken by the vertical haul method. Zooplankton sampling and measurement of water parameters in the form of temperature, pH, and salinity were also conducted to determine the relationship of these parameters with the phytoplankton community. Based on the density of phytoplankton in the water column, the coastal waters of West Bangka are generally in the category of oligotrophic with cell densities ranging from 3.6 × 105 - 1.6 × 107 cells.m-3. The results of the IS-ID analysis showed a difference of 56% in phytoplankton community structures in the mining and non-mining areas of West Bangka coastal. Although no differences were found in the number of phytoplankton genus present, phytoplankton cell density in the waters around the tin mining area was found to be lower compared to the waters in the non-mining area. Differences in community structure and phytoplankton cell density in mining and non-mining areas are thought to be related to mining activities in the coastal. However, further studies are needed to study the magnitude of the influence and exact cause of the emergence of differences in community structure and phytoplankton density.Keywords: Tin mining, spatial distribution, phytoplankton community, Bray-Curtis clustering ABSTRAKPenambangan timah di perairan pesisir Kabupaten Bangka Barat diketahui dapat mempengaruhi kualitas perairan sehingga berdampak pada struktur komunitas fitoplankton. Penelitian ini bertujuan untuk mempelajari komunitas fitoplankton di kawasan tambang timah pesisir (mining) dan di luar area tambang (non-mining) di pesisir Bangka Barat. Pengambilan sampel dilakukan pada bulan Oktober 2012 di 22 stasiun sampling, termasuk 7 stasiun sampling yang berada di area penambangan timah. Sampel fitoplankton diambil dengan metode vertical haul menggunakan jaring Kitahara (mata jaring 80 µm). Pengambilan sampel zooplankton dan pengukuran parameter air berupa suhu, pH, dan salinitas juga dilakukan untuk mengetahui hubungan parameter tersebut dengan komunitas fitoplankton di area kajian. Berdasarkan densitas fitoplankton di kolom air, perairan pesisir Bangka Barat secara umum berada dalam kategori oligotrofik dengan densitas sel berkisar antara 3,6×105 – 1,6×107 sel.m-3. Komunitas fitoplankton di Bangka Barat terdiri atas 28 genus, mencakup 23 genus Diatomae dan 5 genus Dinoflagellata, dengan Bacteriastrum, Chaetoceros, Thalassiothrix, Rhizosolenia, dan Pseudo-nitzschia sebagai genera paling dominan di perairan. Hasil analisis IS-ID menunjukkan perbedaan sebesar 56% pada struktur komunitas fitoplankton di area mining dan non-mining perairan Bangka Barat. Meskipun tidak ditemukan perbedaan pada jumlah genus fitoplankton yang hadir, densitas sel fitoplankton di perairan sekitar kawasan mining timah ditemukan lebih rendah dibandingkan dengan perairan yang ada di kawasan non-mining Kabupaten Bangka Barat. Perbedaan struktur komunitas dan densitas sel fitoplankton di area mining dan non-mining diduga terkait dengan aktivitas penambangan di perairan pesisir Bangka Barat. Namun diperlukan kajian lebih lanjut untuk mempelajari besar pengaruh dan penyebab pasti munculnya perbedaan struktur komunitas dan densitas fitoplankton tersebut. Kata kunci: Tambang timah, distribusi spasial, komunitas fitoplankton, Bray-Curtis clustering
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Pramita Sari Anungputri, Puspita Yuliandari, and Erdi Suroso. "Karakterisasi Sampah di Lingkungan Universitas Lampung." Journal of Tropical Upland Resources (J. Trop. Upland Res.) 1, no. 1 (July 30, 2019): 171–76. http://dx.doi.org/10.23960/jtur.vol1no1.2019.22.
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Persoalan sampah merupakan salah satu masalah penting yang timbul di kawasan Universitas Lampung seiring dengan meningkatnya jumlah civitas akademika di lingkungan kampus. Karakterisasi sampah sangat penting untuk dilakukan untuk mengetahui proses pengelolaan sampah yang tepat guna. Penelitian ini bertujuan untuk mengkaji karakteristik sampah di lingkungan Universitas Lampung. Sampah di lingkungan Universitas Lampung diklasifikasikan menjadi 4 kategori yaitu sampah kering, sampah basah, sampah abu dan sampah jalanan dengan parameter pengujian yaitu pengujian kadar air, densitas dan nilai kalori. Hasil penelitian menunjukkan bahwa sampah kering memiliki kadar air, densitas dan nilai kalori sebesar 4,68%; 55,81 kg/m3 dan 17,6 MJ/kg, sampah basah memiliki kadar air, densitas dan nilai kalori sebesar 87,37%; 902,80 kg/m3 dan 15,90 MJ/kg, sampah abu memiliki kadar air, densitas dan nilai kalori sebesar 4,71%; 81,20 kg/m3 dan 2,89 MJ/kg serta sampel yang terakhir yaitu sampah jalanan memiliki kadar air, densitas dan nilai kalori sebesar 11,11%; 352,25 kg/m3 dan 12,81 MJ/kg.
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Alva W, Silvia Silvia Grandies, Sutrisno Anggoro, and Niniek Widyorini. "KELIMPAHAN BAKTERI HETEROTROF DAN WATER QUALITY INDEX PADA KERAPATAN MANGROVE YANG BERBEDA DI DESA BEDONO, SAYUNG, DEMAK." Management of Aquatic Resources Journal (MAQUARES) 6, no. 3 (April 30, 2018): 215–21. http://dx.doi.org/10.14710/marj.v6i3.20577.
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ABSTRAK Serasah mangrove yang jatuh di lantai mangrove akan di dekomposisi oleh mikroorganisme heterotrof yang memiliki kemampuan mendegradasi serasah mangrove. Tujuan dari penelitian ini adalah mengetahui kerapatan mangrove, total bakteri heterotrof perairan pada beberapa kerapatan mangrove, Indeks Kualitas Air (IKA) serta hubungan kerapatan mangrove dengan total bakteri heterotrof dan Indeks Kualitas Air (IKA) perairan di Desa Bedono, Demak. Penelitian ini menggunakan metode deskriptif, dengan mengukur parameter pendukung yaitu parameter fisika dan kimia, dan melakukan perhitungan kelimpahan bakteri heterotrof menggunakan metode TPC (Total Plate Count). Hasil pengamatan menunjukan bahwa kelimpahan bakteri heterotrof tinggi berkisar antara (2.120-5.620) x 10-6 Cfu/ml pada saat pasang dan 760-4.840 x 10-6 Cfu/ml pada saat surut.. Berdasarkan hasil penelitian dapat disimpulkan bahwa kerapatan mangrove pada Desa Bedono berkisar antara 900-2.400 pohon/Ha; kelimpahan bakteri hetrotrof di Desa Bedono berkisar antara 760x 10-6 Cfu/ml – 5.620 x 10-6 Cfu/ml; Indeks Kualitas Air (IKA) yang didapatkan berkisar antara 33,1-46,93; terdapat hubungan yang berbanding lurus antara kelimpahan bakteri heterotrof dengan kerapatan mangrove, dan hubungan berbanding terbalik antara Indeks Kualitas Air (IKA), kelimpahan bakteri heterotrof dan kerapatan mangrove. Kata Kunci: Bakteri Heterotrof, Kerapatan Mangrove, Desa Bedono, Indeks Kualitas Air ABSTRACT The mangrove litter that falls on the mangrove floor will be decomposed by heterotrophic microorganisms that have the ability to degrade the mangrove litter. This research is purposed to know the density of mangrove in Bedono, Demak; Looking for total heterotrophic bacteria in some mangrove densities in Bedono village, Demak; knowing Water Quality Index (IKA) in Bedono Village; know the relationship of mangrove density with total heterotrophic bacteria, and Water Quality Index (IKA) in Bedono Village, Demak. This study uses a descriptive method, by measuring the supporting parameters of physical and chemical parameters, and calculating the abundance of heterotrophic bacteria using TPC (Total Plate Count) method. The observed results show the high abundance of heterotrophic bacteria ranging between (2.120-5.620) x 10-6 Cfu/ml at high tide and 760-4.840 x 10-6 Cfu/ml at low tide. Based on the results of the research can be concluded that the mangrove density in Bedono village ranged between 900-2.400 trees/Ha; The Water Quality Index (IKA) that occurs is between 33,1-46,93; There is a direct relationship between the abundance of heterotrophic bacteria with mangrove density, and the inverse relationship between the Water Quality Index (IKA), abundance of heterotrophic bacteria and mangrove density. Keywords: Heterotrophic Bacteria, Mangrove Density, Bedono Village, Water Quality Index
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Pangaribuan, Tumpal Hasudungan, Prijadi Soedarsono, and Churun Ain. "HUBUNGAN KANDUNGAN NITRAT DAN FOSFAT DENGAN DENSITAS ZOOXANTHELLAE PADA POLIP KARANG Acropora sp. DI PERAIRAN TERUMBU KARANG PULAU MENJANGAN KECIL, KARIMUN JAWA." Management of Aquatic Resources Journal (MAQUARES) 2, no. 4 (October 29, 2013): 136–45. http://dx.doi.org/10.14710/marj.v2i4.4277.
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Terumbu karang merupakan ekosistem pesisir yang memiliki produktivitas tinggi. Nutrien merupakan salah satu faktor penentu terpeliharanya produktivitas perairan. Adanya asumsi ketersediaan cahaya, keberadaan zooxanthellae dan nutrien menjadi faktor yang penting. Permasalahannya adalah, apakah dukungan ini didapatkan dari ketersediaan nutrien di lingkungan perairan atau di dalam polip karang. Terkait dengan hal tersebut, maka penelitian ini akan mempelajari dukungan nutrien di dalam polip karang dan pengaruhnya terhadap keberadaan zooxanthellae. Tujuan penelitian ini untuk mengetahui kondisi penutupan karang di daerah pulau Menjangan Kecil, mengetahui total nitrat dan total fosfat, densitas zooxanthellae, hubungan kandungan antara total nitrat dan total fosfat terhadap densitas zooxanthellae di polip karang Acropora sp. di perairan terumbu karang pulau Menjangan kecil, Karimun Jawa. Metode yang digunakan adalah metode deskriptif eksplanatif. Hasil penelitian menunjukkan bahwa penutupan karang di perairan pulau Menjangan Kecil stasiun I 73,6% kategori baik dan stasiun II 76% kategori sangat baik. Terdapat hubungan antara kandungan nitrat dan fosfat pada polip karang Acropora sp. dengan densitas zooxanthellae. Pada sampel polip di dapat densitas zooxanthellae sebesar : 44 × 106 sel/ml - 78,5 × 106 sel/ml. Pengukuran nitrat pada sampel polip di dapat hasil sebesar: 14,78% - 21,09%. Pengukuran kandungan fosfat, pada sampel polip di dapat hasil sebesar: 23,4% - 28,18%. Nilai koefisien determinasi R2 antara total nitrat dengan densitas zooxanthellae sebesar 0,939 dimana mengandung pengertian pengaruh total nitrat terhadap densitas zooxanthellae adalah 93,9 %. Koefisien determinasi R2 antara total Fosfat dengan densitas zooxanthellae sebesar 0,514 dimana mengandung pengertian pengaruh total fosfat terhadap densitas zooxanthellae adalah 51,4 %. Hal ini mengindikasi semakin tinggi kandungan nitrat dan fosfat maka semakin tinggi pula densitas zooxanthellae di dalam polip karang Acropora sp. dan parameter kualitas air diukur sebagai data pendukung.
Dissertations / Theses on the topic "Parametro di densità"
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Falo, Francesco. "Nuova misura del parametro di densità della materia dalle distorsioni geometriche nel clustering delle galassie BOSS." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/15438/.
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Uno dei principali obiettivi della cosmologia osservativa moderna è la misura dei parametri del modello cosmologico standard. Tra questi vi è il cosiddetto parametro di densità della materia, Omega. In questo lavoro di Tesi abbiamo utilizzato uno dei più estesi cataloghi spettroscopici di galassie, fornito dalla Baryon Oscillation Spectroscopic Survey (BOSS), per misurare Ωm tramite il test di Alcock-Paczynsky. Nello specifico, abbiamo sfruttato le anisotropie geometriche nella funzione di correlazione a due punti delle galassie, dovute alla scelta di una cosmologia diversa da quella reale nel calcolo delle distanze comoventi. Il risultato ottenuto è un valore di 0.29 per il parametro di densità della materia, consistente con misure indipendenti ottenute in passato sfruttando diverse sonde cosmologiche, quali la radiazione cosmica di fondo e le proprietà spaziali delle strutture a grande scala dell'Universo.
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Evola, Chiara. "Cenni al modello del Big Bang, inflazione e materia oscura." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19481/.
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Questo elaborato vuole offrire un riassunto del modello del Big Bang, della materia oscura e del Modello Cosmologico Standard, come conseguenza dei primi due.
La cosmologia è la scienza che studia l’Universo nel suo insieme, la sua formazione, la sua evoluzione e il suo destino futuro.
Partendo dalle scoperte osservative, che hanno permesso la teorizzazione dell'espansione dell'Universo, Lemaȋtre, nel secolo scorso, getta le basi per il primo modello del Big Bang. Quest'ultimo mira a spiegare come si sia generato il nostro Universo. Nel tempo i cosmologi hanno reso il modello sempre più complesso e accurato, anche grazie alle numerose scoperte astronomiche dell'ultimo secolo.
Tra queste scoperte c'è la materia oscura, un elemento fondamentale del nostro Universo, e uno dei dilemmi più grandi dell'astrofisica dei nostri giorni. All’interno di questo elaborato ne è illustrato il percorso storico, tra le osservazioni e le ipotesi legate alla sua origine e alla sua composizione.
Infine, viene accennato il Modello Cosmologico Standard e i suoi parametri. Il modello che ad oggi è accettato dalla comunità scientifica.
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Asciutto, Emanuele. "Dinamiche spaziotemporali del merlano (Merlangius merlangus, Linnaeus 1758) nel Mar Adriatico centro-settentrionale." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23110/.
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Le caratteristiche fisiche e ambientali dello spazio influenzano la disposizione degli organismi. La distribuzione e la densità delle specie possono subire dei mutamenti spaziotemporali a causa di plurimi fattori, sia biotici che abiotici. Conoscere i tratti ecologici degli organismi e comprendere come essi reagiscano a questi fattori è fondamentale per fare predizioni sulle possibili condizioni future delle loro popolazioni. La specie oggetto di questo studio è il merlano (Merlangius merlangus) un pesce molto comune nel Mare del Nord, in Adriatico centro-settentrionale, nell’Egeo e nel Mar Nero, localmente anche importante sul mercato. Attraverso il programma di ricerca Mediterranean Trawl Survey (MEDITS), che prevede monitoraggi annuali di pesca a strascico scientifica, è stato possibile più informazioni su questa specie che, in Adriatico, risulta essere poco studiata. I dati ottenuti coprono gli anni che vanno dal 1994 al 2020. Essi sono stati analizzati al fine di trarre informazioni sulla struttura per classi di taglia, sugli effetti di variabili ambientali quali profondità e temperatura sulla densità, sulla distribuzione spaziale della densità e stime annuali della stessa. I risultati evidenziano come le taglie predominanti in ogni anno raramente raggiungano i 20cm corrispondenti al primo anno di età, ma si attestino in media intorno ai 10-15cm con una tendenza verso taglie maggiori a fine estate/inizio autunno. I modelli Generalized Additive Models (GAMs) impiegati nelle analisi statistiche mostrano come M. merlangus pare preferire temperature inferiori a 20°C e profondità fino a 100 metri. Negli anni non si sono evidenziate tendenze positive o negative della densità, ma picchi e valli più o meno alternati. L’Adriatico settentrionale è risultata l’area maggiormente caratterizzata dalla presenza di M. merlangus. La raccolta di informazioni di questo tipo consente di gettare le basi per indagini più specifiche di valutazione dello stato di questa risorsa.
Books on the topic "Parametro di densità"
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Di qiu zheng chang mi du jia shuo: Zhong li xue de can shu tuo qiu yu wei xiang mi du li lun = Hypothesis of the earth's normal density : the gravity theory of parameter spheroid and latitudinal density. Beijing: Ce hui chu ban she, 2009.
Find full textConference papers on the topic "Parametro di densità"
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Chen, Ronghua, Gunaghui Su, and Suizheng Qiu. "Analysis of CHF Characteristics of Concentric-Tube Open Thermosyphon by Using Artificial Neural Network." In 18th International Conference on Nuclear Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/icone18-29707.
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An artificial neural network (ANN) for predicting critical heat flux (CHF) of concentric-tube open thermosyphon has been trained successfully based on the experimental data from the literature. The dimensionless input parameters of the ANN are density ratio, ρl/ρv, the ratio of the heated tube length to the inner diameter of the outer tube L/Di, the ratio of frictional area, di/(Di + do), and the ratio of equivalent heated diameter to characteristic bubble size, Dhe/[σ/g(ρl−ρv)]0.5, the output is Kutateladze number, Ku. The predicted values of ANN are found to be in reasonable agreement with the actual values from the experiments with a mean relative error (MRE) of 8.46%. For a particular outer tube, the CHF increases initially and then decreases with increasing inner tube diameter, and has a maximum at an optimum diameter of inner tube (do,opt). The do,opt is correlated with the working fluid and may decrease with the increase of ρl/ρv. CHF decreases with the increase of L/Di, and the decreasing rate decreases as L/Di increases. In the influence scope of pressure, the CHF decreases with increasing pressure for R22, while increases with increasing pressure for R113.
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Bhunia, Avijit, Ya-Chi Chen, and Chung-Lung Chen. "Impact of Surface Micro-Structures on Liquid Micro-Jet Array Impingement Cooling: Comparison Between Single-Phase and Phase Change Heat Transfer." In ASME/JSME 2011 8th Thermal Engineering Joint Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajtec2011-44490.
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This article investigates liquid micro-jet array impingement cooling of a micro-structured surface. An array of 16 free-surface DI water jets, each 125 μm in diameter, and jet Reynolds number ranging between 816 and 2124, is used. A parametric study is carried out with micro-studs of varying size and spacing, implemented on a 1 cm2 base area surface. Based on the decades of research on heat transfer enhancement by surface modification, one would intuitively think that impingement cooling of a micro-structured surface will always be better than that of a plain surface. The current results are in contrary. The micro-structures actually degrade single-phase impingement heat transfer, compared to a plain surface. On the other hand, in the phase change regime they significantly enhance heat transfer, leading to a clear choice of optimal structure. The results are explained in the light of thin film dynamics, heat transfer surface area enhancement and nucleation site density.
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Sammartano, Giulia, Mattia Previtali, and Fabrizio Banfi. "PARAMETRIC GENERATION IN HBIM WORKFLOWS FOR SLAM-BASED DATA: DISCUSSING EXPECTATIONS ON SUITABILITY AND ACCURACY." In ARQUEOLÓGICA 2.0 - 9th International Congress & 3rd GEORES - GEOmatics and pREServation. Editorial Universitat Politécnica de Valéncia: Editorial Universitat Politécnica de Valéncia, 2021. http://dx.doi.org/10.4995/arqueologica9.2021.12155.
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In the wide framework of Scan-to-BIM 3D modelling procedures, the complexity of the architectural heritage and its components is evidencing a gap of best practices and specification in the HBIM-modeling and thus it is requiring important considerations about the modelling strategies and protocols between the requested level of detail (LOD), the expect accuracy and above all the actual use-oriented requirements. Several works are largely focusing on developing workflows for traditional static LiDAR scanning sensors. However, the chance to benefit from on-site faster data acquisition is needful at times, and procedures are directing toward rapid mapping 3D approaches, evolving from traditional static scanning toward MMS (Mobile Mapping Systems) based on SLAM technology (Simultaneous Localization and Mapping) algorithms implemented in portable devices. The potential of these solutions can contribute to increase a massive cost-effective documentation, and also in view of BIM-HBIM modelling generation, and this needs further researches. At the same time, the descriptive capabilities of this class of portable scanners do not reach the precision of the static solutions. Many time-cost balance evaluations towards an analysis of geometry, grade of generation (GOG) and details can be thus conducted. This paper presents a first comparison between TLS (Faro Focus 3D) and hand-held scanner Zeb Revo (by GeoSLAM) of the entire workflow (from raw data acquisition up to parametric modeling) focusing on the Bramante’s Canonica Court in the Basilica di Sant’Ambrogio. First, the two raw data are compared, considering geometric features (data density, precision, possibility to detect edges, details and accurate curvature). Then, some well-established modelling procedures developed for TLS data, as triangulation mesh and NURBS generation, are applied to MMS point cloud to identify their suitability. Different elements belonging to the architectural structure hierarchy are considered in a multi-scale perspective: the vaulted system of the porch, the columns and the arches of the porch with their different architectural elements.
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Kellie, Benjamin, and Shaurya Prakash. "Fabrication of Ceramic High Temperature Microsystems." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-64476.
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This paper reports on recent advances in fabricating alumina-based ceramic microcombustors for applications in high temperature microsystems. We have fabricated alumina structures with critical dimensions on the order of 1 mm or less by using a gel-casting approach with poly(vinyl) alcohol (PVA) as a non-toxic polymeric binder. Polymer binder content, alumina weight ratio, and thermal cycling were varied systematically to develop microcombustors that can sustain stable flames in a spiral configuration allowing for better mixing of fuel and oxidizer streams for a more uniform heat output. The polymer binder and cross-linker content varied between 10 and 20% (w/v to DI water) and 50 and 100% (w/w to PVA) respectively to obtain an optimal binder content. The weight ratio of alumina (w/w 30–50%) in the binder solution was evaluated with 1.1 micron particles to observe the effect on the green body density. The green body was then fired in a high temperature furnace in air to burn-out the polymeric binder and sinter the ceramic. Heating and cooling rates, maximum operation temperature, and dwell times were evaluated to obtain high density ceramic structures with 50% or higher alumina content. Thermal stress and heating and cooling rates appear to be major parameters to control in order to obtain high-quality microcombustors.
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Sciacovelli, Adriano, Vittorio Verda, Cristina Amelio, Carlo Repetto, and Gustavo Diaz. "Performance Improvement of a Circular MCFC Through Optimal Design of the Fluid Distribution System." In ASME 2011 9th International Conference on Fuel Cell Science, Engineering and Technology collocated with ASME 2011 5th International Conference on Energy Sustainability. ASMEDC, 2011. http://dx.doi.org/10.1115/fuelcell2011-54436.
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In this paper, the prototype of a circular Molten Carbonate Fuel Cell (MCFC) built in the laboratories of FN SpA Nuove Tecnologie e Servizi Avanzati is analyzed using a tridimensional computational fluid dynamic (CFD) model. The prototype is the result of FN and Politecnico di Torino activities developed for the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) within the framework of Ministry of Economic Development, MSE-ENEA. This model considers heat, mass and current transfer as well as chemical and electrochemical reactions. The results show that some inhomogeneous distributions in the reactants, causing non-optimal use of the reactant surfaces. An effective way to improve the distribution in current density consists in tracing tree shaped channels on the surface onto the distribution porous medium. In this paper Y shaped channels are adopted to improve the distribution of gas within the fuel cell and consequently to enhance the performance of the original design of the fuel cell. In addition, the configuration of the outlet of the anodic compartment is also investigated in order to further increase the performance of the fuel cell. The geometrical parameter identifying the topology of distribution channels are chosen accordingly to the constructal theory. The results show that significant improvements can be achieved. Power density is increased of about 6% when the tree-shaped channel is adopted. If a double anodic inlet is also considered the enhancement in the power density is of about 11% with respect to the initial configuration.
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Bassi, F., S. Rebay, and M. Savini. "Quasi-3D Numerical Computations on a Film-Cooled Gas Turbine Nozzle." In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-536.
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The aim of this work is to assess the accuracy of a “quasi-3d” Navier-Stokes solver equipped with the k-ω turbulence model in the computation of a film-cooled gas turbine blade under a variety of flow conditions. The “quasi-3d” formulation was chosen as a cheap approach to investigate a large number of test conditions for a nozzle of complex geometry (around 400 cooling holes) which would require a large computational effort for a truly 3d simulation. The developed code has been used to investigate the influence of various cooling geometries and blowing conditions (mass flow rate and/or density ratios) on the aerodynamic behaviour of the cascade (in terms of loading, losses and flow angles) and their impact on the mixing process downstream of the trailing edge. The investigated nozzle is an advanced design turbine vane working in high subsonic regime. It is characterized by a marked endwall contouring at the casing and by the presence of 12 rows of holes (including a trailing edge row of slots) so as to obtain full-coverage film-cooling of the solid surfaces. This vane has been extensively tested in the Politecnico di Milano Fluid Dynamics Laboratory (formerly C.N.P.M.) blowdown transonic wind tunnel and a great amount of data are therefore available for validation purposes. The uselfulness of the proposed approach is fully analyzed and discussed throughout the paper and it is shown that the relation between the cascade performance and the variation of the investigated parameters is correctly described. In addition we address and discuss which ejection boundary conditions and which loss definitions are best suited for a meaningful comparison with the experimental measurements. In conclusion, in the case considered the developed code seems to be a valuable tool to determine the impact of film-cooling on the aerodynamic performance of a gas turbine blade.
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Ciatti, Stephen, Swami Nathan Subramanian, and Alison Ferris. "Effect of EGR in a Gasoline Operated Diesel Engine in LTC Mode." In ASME 2012 Internal Combustion Engine Division Spring Technical Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ices2012-81010.
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Conventional combustion techniques struggle to meet the current emissions’ regulations while retaining high engine efficiency. Specifically in automotive diesel engines, oxides of nitrogen (NOx) and particulate matter (PM) emissions have limited the utilization of diesel fuel in compression ignition engines. By comparison, throttled, knock-limited conventional gasoline operated SI engines tend not to be fuel efficient. Advanced combustion systems that simultaneously address PM and NOx while retaining the high efficiency of modern diesel engines, are being developed around the globe [1]. One of the most difficult problems in the area of advanced combustion technology development is the control of combustion initiation [2] and retaining power density [3]. During the past several years, significant progress has been accomplished in reducing emissions of NOx and PM through strategies such as LTC/HCCI/PCCI/PPCI and other advanced combustion processes; however control of ignition and improving power density has suffered to some degree — advanced combustion engines tend to be limited to the 10 bar BMEP range and under [4]. Experimental investigations have been carried out on a light duty, DI, multi cylinder, diesel automotive engine. The engine is operated in low temperature combustion technology with 87 RON (Research Octane Number) fuel [7]. Using an Ignition Quality Test (IQT) device, the equivalent Cetane Number (CN) was measured to be 25. In the present work, various EGR rates are examined to determine the effect on the combustion, emissions and performance. Experiments were conducted at three different engine load/speed combinations that are part of General Motors’ reference points for vehicle operation. To reduce the complexity, boost pressure and injection pressure and timing were kept constant while EGR percentage and intake temperature were used as parameters in this study. The intake temperature was not truly independent, as it trended with EGR level, but based upon the boost level and the available EGR cooling, Intake Air Temperature (IAT) was kept in the range of 40–80 deg C. Additional cooling capacity will be added in future work in an effort to keep IAT more consistent. EGR rates have a detrimental effect on engine efficiencies at lower load while it appears to have little effect on efficiency at higher loads. A more significant effect at very low load appears to be higher intake temperatures (hot EGR) as opposed to the very slight decrease in oxygen concentration.
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Baratta, Mirko, Andrea E. Catania, and Francesco C. Pesce. "Computational and Experimental Analysis of Direct CNG Injection and Mixture Formation in a Spark Ignition Research Engine." In ASME 2010 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/icef2010-35103.
Full textAbstract:
Direct injection (DI) of compressed natural gas (CNG) under high pressure conditions is a topic of great interest, owing to its potential for improving SI engine performance and fuel consumption. However, relevant technical difficulties have yet to be resolved in order to stabilize combustion process, especially for stratified engine operating conditions. The present paper is focused on experimental and numerical investigations of the jet formation and fuel-air mixing process in a research optical-access single-cylinder engine. The engine is based on the multi-cylinder engine under development within the European Community (EC) VII Framework Program (FP) InGAS Integrated Project, and features a centrally mounted poppet-valve injector on a pent-roof combustion chamber with a bowl in piston. Experimental investigations were made by means of the planar laser-induced fluorescence technique, and revealed a cycle-to-cycle jet shape variability. In particular, for specific cylinder pressure values at the start of injection, the jet can adhere to chamber walls for a relevant number of cycles, leading to an ‘umbrella-like’ shape. This can change the mixing capabilities of the combustion chamber and cause instabilities in the combustion process. The mentioned behaviour is strongly dependent not only on the injection and cylinder pressures, but also on important design parameters, such as needle cone angle and in-chamber injector protrusion. For this reason, in order to obtain a deep insight into the injected gas behaviour on an average cycle basis, the experimental investigation was supported by a numerical analysis. Simulations were carried out by an optimized variable-density finite-volume numerical model which was built within the Star-CD environment. A previously developed and validated ‘virtual injector’ model was implemented. The outcomes of the numerical model were compared to laser-induced fluorescence images, for both stratified- and homogeneous-charge engine operating conditions and a good agreement was obtained, substantiating the reliability of the applied computational model. Then, the effects of the injector protrusion in the combustion chamber and of injection timing were analyzed, and their impact on jet stability and mixture-formation process was analyzed.