Pages 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 14897 result(s) returned

2.1 What is energy?

'Energy is Eternal Delight'

William Blake, 1757–1827 (1994)

What do we mean by 'energy'? What does the concept of 'sustainability' entail? And what, for that matter, do we mean by the 'future' in this context?

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1.1.1 Where do we get our energy from?

The world's current energy systems have been built around the many advantages of fossil fuels, and we now depend overwhelmingly upon them. Concerns that supplies will 'run out' in the short-to-medium term have probably been exaggerated, thanks to the continued discovery of new reserves and the application of increasingly advanced exploration technologies. Nevertheless it remains the case that fossil fuel reserves are ultimately finite. In the long term they will eventually become depleted and
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6.3 Sustainable development

The third approach to balancing human needs with environmental protection is to try to come to grips with what we mean by sustainability.

The most widely quoted definition of sustainable development is the one used by Gro Harlem Brundtland in the highly influential book Our Common Future (Brundtland, 1987):

'Sustainable development is development that meets the needs of the present withou
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Keep on learning

Study another free course

There are more than 800 courses on OpenLearn for you t
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Structural devices
Microelectronics has enabled designers of integrated circuits to exercise complete control over the electrical characteristics of each component they create. This free course, Structural devices, will illustrate how such control is achieved and the various methods that can be applied in differing circumstances. First published on Tue, 07 May 2019 as
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Except for third party materials and otherwise stated (see http://www.open.ac.uk/conditions terms and conditions), this content is made available under a http://creativecommons.org/licenses/by-nc-sa/2

Introduction

In this course we examine one factor that very often seems to be found skulking around close to problems and solutions: temperature.

Almost whatever we do, wherever we are, temperature changes. Stay in the same spot and you'll find daytime and night-time temperatures can be markedly different. You may even find significant changes in temperature during the day. When moving you can encounter more rapid variations. For example, an aircraft might leave a tropical runway where the air tempe
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3.1 (4A) Exploring dynamic relationships using sign graphs

Here is where things start getting really interesting in terms of system dynamics! So far, most of your modelling work has been pretty static, with a limited sense of how things change over time. In fact, the behaviour of complex systems is rarely stable. Sometimes change is exponential (e.g. the growth of the World Wide Web); sometimes systems crash and burn (e.g. extinction of populations); but often systems demonstrate repetitive patterns of behaviour (e.g. economic boom and bust cycles).
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2.5 Interdependence

The first step in transforming the way you think involves coming to terms with the fact that you are not an independent, isolated object, but rely on Author(s): The Open University

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3.1 The steps to systems modelling

Systems modelling in practice usually involves six broad steps, within each of which there may be many subsidiary steps and some checking and revision. There is also likely to be iteration back to the earlier steps, as issues which call for changes in earlier decisions are uncovered.

Nevertheless, in my experience, the following six steps are likely to cover the basics.

  1. Identify the system of interest, in particular specify the system boundary a
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Stage 5: Formulating measures of performance (how will we know when we have arrived?)

The hard systems approach emphasises the need to have measurable means of assessing the efficacy of any potential solution or design, but recognizes that this may not always be possible.


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3.7 Systems methodologies for managing change

The use of systems concepts and models forms part of a process of investigation that is often described in the literature of systems, design and decision-making as a ‘methodology’, where a methodology is a process of enquiry, not a method to produce a predetermined result.

A systems methodology has the following characteristics.

  • It is, or it provides, the means for the investigator to draw up a plan for studying a situation. This encourages
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1.5 Increasing complication, complexity and risk: the underlying relationship

Figure 3 showed five commonly encountered problems of effecting different types of change. These are notionally located on a spectrum of change that ranges from no change at all, to complete revolution. The relationship suggested on the figure is that as the degree of change – represented
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1.3 Example 1 The Workcenter that didn't

Autodesk Inc. is the world's largest supplier of design and engineering software. It currently markets over thirty products but is most famous for its AutoCAD® two- and three-dimensional design and drafting software. The company is the market leader in this type of application, with over 4 million customers worldwide.

The Autodesk story began in 1982 with a group of programmers, centred on San Francisco, writing code for design software in their spare time. The group demonstrated a cob
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1.1 Introduction: what is the problem?

In late June and early July 2005 a row erupted concerning the operation of a major flagship of government social policy, the tax credit system. Introduced in 2003, it was designed to help those on low incomes and whose social circumstances prevented them from working full-time (Citizens Advice Bureau, 2005). The article reprinted in Box 1 indicates the extent of the political unrest with a system that left families relying on food parcels, and that has been variously described as being ‘in
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Conclusion

This free course provided an introduction to studying Computing & IT. It took you through a series of exercises designed to develop your approach to study and learning at a distance, and helped to improve your confidence as an independent learner.


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3.2 Making sense of the metaphor

The metaphor of the juggler keeping the four balls in the air is a powerful way for me to think about what I do when I try to be effective in my practice. It matches with my experience: it takes concentration and skill to do it well. But metaphors conceal features of experience, as well as calling them to attention. The juggler metaphor conceals that the four elements of effective practice often seem to be related. I cannot juggle them as if they were independent of each other. I can imagine
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8.5 Review

We can sum up the distinctive features of wet etching with a few key points:

  • Wet etching, in general, is a simple process to operate. Wafers are immersed in a solution for a while before being taken out, rinsed, and dried. However, certain etches require more sophistication. They may need one or more of the following: heating and agitation of the solution; reflux of vapours to maintain concentrations; protection of back side of the wafer; incorporation
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8.4.1 Open-loop control

Open-loop is the crudest way of controlling etch depth. It relies on ensuring that every aspect of the process that can affect the rate of progress of the etch is kept under tight control. This can add up to a sizeable list. Table 5 shows just some parameters that affect both wet and dry etching.

Whethe
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