Bend allowance

DNA binding by TBP is strongly dependent on the presence of T-A base pairs in the TATA box. Bending allows remote sites on the DNA, with their bound cognate specific transcription factors, to come close together such that the proteins can interact to form the transcriptional preinitiation complex. 

A tabulated form as in Table 19.3. This shows flows versus pipe length and diameter for both copper and steel. Such tables are included in British Gas lM/16 and British Standard BS 6891. Note that Table 19.3 includes allowances for elbows, tees and bends. Allowances, equivalent to numbers of pipe diameters, must be made for all pipe fittings, which cause an additional pressure loss. Further details for allowances to be made for pipefittings, including valves and nonreturn valves, are given in Table 19.4. 

Unlike the single-crystal electrodes in which band bending allows efficient charge... 

X-Ray crystallographic analysis of two crystalline forms of tetrameric melittin showed that the conformation of the peptide is essentially the same in each form. " Melittin was found to adopt a helical conformation in the crystalline state. The presence of Pro-14 also caused the helix to bend with an angle of about 120° between residues 1-10 and 16-26. The large helix bend allows for the optimal packing of hydrophobic side-chains vnthin the tetramer. Melittin provides a rare example of a membrane-bound peptide whose structure has been determined in low dielectric solvents, micelles and in the crystalline state and found to be quite similar. The similarities of these structures lends confidence to the idea that they represent good models for the membrane-bound conformation. ... 

The CH chromophore is composed of mode 1 (CH stretch) and mode 5 (HCD bend) whose fundamental frequencies are 2,990 cm 1 and 1,293 cm, respectively. The remaining four modes are called bath modes. (These modes are described further in Ref. 95.) The fundamental energies of the CH stretch and CH bend allow a strong Fermi resonance between the Inv,)0 and ( — m)v, + 2mv5)° zero-order states. If n is larger than 4, the difference in the energies of the zero-order states, i.e., v,)° and (/i — m)v. 

As an effect of the bend radii the unfolded dimensions of a blank cannot be determined as the sum of the over measured flange dimensions. The difference between both is referred to as the bend allowance BA). The BA can be determined experimentally. For mild steel the DIN6935 standard also offers a series of heuristic formulas. The standard uses the assumption that the neutral fibre (fibre with no effective strain) is showing... 

Based on the DIN 6935 formulas the bend allowance BA can be determined using this... 

To find the development length on the flat sheet, it is necessary to find the length of the mean line by calculating the lengths of the flat portions and the bends separately. The stretched-out length of the bend is called the bend allowance and for a 90° bend is found by multiplying the mean radius by 1.57 (i.e. n/2). 

It can be seen that the development of the bracket shown in Fig. 4.15 is made up of a 57 mm straight length plus a bend allowance of 4 mm plus a further straight length of 77 mm as shown in Fig. 4.16. The bend is half way across the bend allowance, and therefore the bend line must be 57+2=59mm from one edge. 

Special construction features are represented as special information in the model. A few of them from industrial practice are as follows zero radius bends allow for the modeling of bends that do not have an interior bend radius zero degree bends represent edge connections where brazing or welding is specified instead of bending 180° bends represent reinforcement bends. 

Material growth for the flat pattern, or bend allowance or K-factor is calculated for the material, thickness, and machine information of each bend using generally applicable and user-specific bend tables and equations automatically. 

The starting width of the strip is narrower than the theoretical width calculated from the neutral axis (half-thickness) of the curved elements. For the purpose of accurate blank size calculation, it is assumed that the neutral axis moves from the half-thickness position closer to the inside of the bent element. The new location of the relocated neutral axis is expressed by the bend allowance k factor). For example, for low-carbon, annealed steel having a bending radius equal to material thickness, the k factor is about 0.33. In this case, k = 0.33 means that the new neutral axis used to calculate the blank size will be 0.33 times the metal thickness distance from the inside surface of the bent element (instead of 0.5 times the metal thickness), as shown in Fig. 12. 

Figure 12 Bend allowance k factor) is used to calculate blank width.

Some computer programs, in addition to the roll drawings, also provide tool cost estimates, bill of materials for the roll blanks, and prepare setup charts. More sophisticated programs also provide stress calculations to indicate potential problems before rolls are cut. Several computer-aided systems provide guidelines for the number of passes and calculate bend allowances. 

Bend Allowance—The actual amount of material used in the bend the length of the neutral axis of the bend. 

Bend Deduction (also called the Bend Reference or the K-Factor)—The amount of material equal to that gained in measurement by deformation due to bending. This number is calculated by subtracting one bend allowance from two mold legs. 

The bend allowance is calculated by taking the length of the arc with a radius of one bend radius plus 0.445 times the material thickness (remember that 0.445 is the percentage of the material thickness for the neutral axis). Because the formula for the circumferance of a circle is lirr, with r being equal to the radius, we just multiply this by the portion of the circle with which we are dealing (in this case, 90/360 or 0.25). Representing bend allowance by BA, we get... 

Entering our information into these formulas, we get a bend allowance equal to 0.203. 

The bend deduction is calculated by taking two times the mold leg and subtracting one bend allowance. Representing the bend deduction by K (see vocabulary list), we get... 

In most cases, the only numbers that will be needed are the mold leg, the bend allowance, and the bend deduction. The other numbers tU e used primarily when parts are dimensioned in an unusual manner. In most cases, dimensions are given to the mold point or the center of radius. It is also common to see dimensions to the inside of the material on 90° bends. 

L is unstable relative to B2 simply because bending allows an electron... 

The theory developed by Volkersen takes no account of two important factors. First, the directions of the two forces P in Figs 7 and 8(a) are not colinear. There will therefore be a bending moment applied to the joint in addition to the in-plane tension. Secondly the adherends bend, allowing the joint to rotate as shown in Fig. 6(b). 

Thus nitrogen NMR can monitor reactions in which the shift of a -electron pair onto nitrogen, as it bends, allows the metal to accept an incoming ligand (and the nitrogen to coordinate a proton or other Lewis acid). A comparable -electron pair shift onto nitrogen is also possible in imido and nitrido ligands. ... 

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