Kajian Total Biomassa Rerumputan Dan Pengaruhnya Terhadap Tata Air Tanah Di Daerah Tangkapan Air Danau Toba. Studi Kasus Di Kecamatan Silahisabungan Kabupaten Dairi

The study on the total of biomass of grasses and it\u27s influences on soil moisture was conducted atSilahisabungan Subdistrict Dairi District, from November 2011 until February 2012. The objectiveof this research was to evaluate the effect of grasses to soil mositure. This study used survey methodwith purposive sampling. The result of this research showed that grass vegetation with rathersloping class total biomass 10,6 ton/ha, carbon reserve 5,3 ton/ha, field capacity 63,4 %, permanentwilting point 1,3 %, water content 62,0 % and permeability 7,5 cm/hours. In the undulating slopestotal biomass 7,1 ton/ha, carbon reserve 3,55 ton/ha, field capacity 51,6 %, permanent wiltingpoint 2,4 %, water content 49,2 % and permeability 7,6 cm/hours. In the rather steep slope totalbiomass 15,5 ton/ha, carbon reserve 7,75 ton/ha, field capacity 32,8 %, permanent wilting point 3,8%, water content 29,0 % and permeability 9,6 cm/hourd. In the forest vegetation with rather slopingclass, biomass total 7,54 ton/ha, carbon reserve 3,77 ton/ha, field capacity 150 %, permanent wiltingpoint 23,5 %, water content 126,5 % and permeability 10,3 cm/hours. In the undulating slopes totalbiomass 6,24 ton/ha, carbon reserve 3,12 ton/ha, field capacity 51,5 %, permanent wilting point 7,5%, water content 44 % and permeability 8,2 cm/hours. In the rather steep slope total biomass 8,86ton/ha, carbon reserve 4,43 ton/ha, field capacity 33,3 %, permanent wilting point 4,2 %, watercontent 29,2 % and permeability 11,25 cm/hours

Investigation of Aluminum-Stainless Steel Dissimilar Weld Quality using Different Filler Metals

Aluminum-stainless steel dissimilar welding processes yield unwanted disadvantages in the weld joint due to the large difference between the aluminum-stainless steel sheets’ melting points and the nearly zero solid solubility between these two metals. Aluminum AA6061 and stainless steel SUS304 were lap-welded by using Metal Inert Gas (MIG) welding with aluminum filler ER5356 (Group 1) and stainless steel filler ER308LSi (Group 2). The effects of the welding voltage and type of filler metals used on the weld joints were studied. The welding voltage had a significant effect on the welding process, as higher voltage resulted in poorer appearance of the weld joint and led to defects for both groups, such as porosity and incomplete fusion. The microstructure for Group 1 joints shows enrichment of Si particles, which benefited the joint properties as it increased the strength of the metal. The stainless steel substrates that spread into the aluminum side are much greater in volume for Group 1 than for Group 2 joints. Meanwhile, the microstructure of Group 2 joints (using ER308LSi filler) consists of chromium carbide precipitation which yields a high hardness value, but a brittle structure. The hardness values of the welded seams in Group 1 and Group 2 range from 60 to 100 HV and 160 to 230 HV, respectively. The fracture in the tensile test yielded the highest tensile strength of 104.4 MPa with aluminum fillers. The tensile strength of Group 1 joints ranging from 47.8 to 104.4 MPa was collectively higher than Group 2 joints, between 20.24 to 61.76 MPa. Based on the investigation throughout this study, it can be concluded that the welding voltage of 18 V and aluminum filler ER5356 is the optimum filler in joining the dissimilar metals aluminum AA6061 and stainless steel SUS 304

Development of a new machine system for the forming of micro-sheet-products

Most of the developed micro-forming machines were based on standalone concepts which do not support efficient integration to make them fully automated and integrated. At present, material feeding in micro-forming is not of sufficient precision and reliability for high throughput manufacturing applications. Precise feeding is necessary to ensure that micro-parts can be produced with sufficient accuracy, especially in multi-stage forming, while high-speed feeding is a must to meet the production-rate requirements. Therefore, design of a new high-precision and high-speed feeder for micro-forming is proposed. Several possible approaches are examined with a view to establishing feasible concepts. Based on the investigation, several concepts for thin sheet-metal feeding for micro-forming are generated, they being argued and assessed with applicable loads and forces analysis. These form a basis of designing a new feeder

Mechanical Strength Of Dissimilar AA7075 and AA6061 Aluminum Alloys Using Friction Stir Welding

The present study focuses on the effects of material position and tool rotational speed on the tensile strength of dissimilar AA7071 and AA6061 welded aluminum alloys with a thickness of 2.0 mm in using a conventional milling machine. Ten joints were produced by varying tool rotational speeds and by changing the fixed position of the material on the advancing and retreating sides. The results show that the maximum tensile strength of 207 MPa was achieved for Sample E when AA6061 aluminum alloys were placed on the advancing side at a rotational speed of 1000 rpm with seamless surface appearance and no inner defect across the weld area, while the lowest tensile strength of 160 MPa was obtained for Sample F when AA6061 was placed on the retreating side with severe tunnel defects across the weld area contributing to crack propagation. Thus, in dissimilar welding, weaker materials should be placed on the advancing side to trigger heat from the tool rotation and smooth the material flow formation in the stirred zone

A new piston referencing algorithm for qualitative assessment of free-piston engine generator performance

Free-piston engine generator (FPEG) provides a novel method for electrical power generation in hybrid electric vehicle applications. This paper presents a new piston positioning method for assessing the performance of a dual-piston type FPEG. Numerical simulations were conducted to obtain motion profiles necessary for the algorithm development. A flowchart for the algorithm was produced. The new piston referencing is named cyclic position which illustrates similar crank-angle-based referencing employed for conventional crank slider engine applications. The results demonstrated cyclic position as qualitative tool for FPEG performance assessment which can be used for data-acquisition user interface in experimental investigations

Substrate and cofactor binding interaction studies of galactitol -1- Phosphate 5- Dehydrogenase from Peptoclostridium difficile

Tagatose is a high value low calorie sweetener that is used as a sugar substitute in the food and pharmaceutical industry. The production of tagatose requires the conversion of galactitol-1-phosphate to tagatose-6-phosphate by galactitol-1-phosphate 5-dehydrogenase (PdGPDH). Theobjective of this work is to study the protein-ligand interaction between PdGPDH and its ligands; galactitol-1-phosphate, Zn2+ and NAD+. Understanding of this mechanism will provide an insight into the possible catalytic events in these domains, thus providing information for potential protein engineering to improve the tagatose production. A 3D model of PdGPDH was constructed to identify the catalytic and coenzyme binding domains. In order to understand the interaction of PdGPDH with its ligands, a docking analysis of PdGPDH-substrate, PdGPDH-Zn2+ and PdGPDH-NAD+ complex was performed using CDOCKER in Discovery Studio 4.0 (DS 4.0). A series of docking events were performed to find the most stable binding interaction for the enzyme and its ligands. This study found that Cys 37, His 58, Glu 59, Glu 142 residues from PdGPDH form an active site pocket similar to known GPDH. A catalytic Zn2+ binding domain and a cofactor NAD+binding domain with strong hydrogen bonding contacts with the substrate and the cofactor were identified. The binding pockets of the enzyme for galactitol-1-phosphate, NAD+ and Zn2+has been defined. The stability of PdGPDH with its ligand was verified by utilizing the molecular dynamic simulation of docked complex. The results from this study will assist future mutagenesis study and enzyme modification work to improve the tagatose production

Diagnosing students' difficulties in learning mathematics

This study considers the results of a diagnostic test of student difficulty and contrasts the difference in performance between the lower attaining quartile and the higher quartile. It illustrates a difference in qualitative thinking between those who succeed and those who fail in mathematics, illustrating a theory that those who fail are performing a more difficult type of mathematics (coordinating procedures) than those who succeed (manipulating concepts). Students who have to coordinate or reverse processes in time will encounter far greater difficulty than those who can manipulate symbols in a flexible way. The consequences of such a dichotomy and implications for remediation are then considered

Carbon nanotube capacitance model in degenerate and nondegenerate regimes

In this work, fundamental results on carrier statistics in a carbon nanotube treated as a one-dimensional material are presented. Also the effect of degeneracy on the capacitance of the carbon nanotube channel in a carbon nan-otube field effect transistor is discussed. A quantum capacitance as well as a classical capacitance is revealed. Furthermore it is shown that for low gate voltage, the total capacitance is equivalent to the classical capacitance but for high gate voltage it is equivalent to the quantum capacitance. We predict that in the nondegenerate regime, the total capacitance is equivalent to the classical capacitance and that the quantum capacitance can be neglected, whereas only quantum capacitance needs to be taken into account in the calculation of the total capacitance in the degenerate regime