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Technical Tennis


Foreword Several years ago, the two authors 0f this b00k and I wrote an encyclopedic tome with the imposing title The Physics の ld 阨 c ん 1 司 0 可 阨 れ ⅲ s. Even though thousands of copies 0f this book have been sold and are still selling, and in spite Of the fact that it was a Scientific American BOOk Club selection, it is not for everyone, and only the 1 れ OSt motivated have read it fror れ cover tO cover. 从 市 0 ever thought there was so much science to hitting a fuzzy yellow ball? Butthere is, and it is all there ⅲ its 435 , 8.5 ' ' x 11" pages, including many hun- dreds Of graphs, charts, diagrams, and formulas. lt is a tremendous reference bOOk, textbook, or self-teaching manual, but it is not a casual read. What is needed now is an up-to-date, reader-friendly book that covers the technical parts Of tennis in a far less comprehensive and technical manner. lt needs tO be written SO that a tennis player can pick it up, read it, and under- stand it. This is that bOOk. lt is written for tennis players and tennis fans, not engineers, scientists, over-motivated super-achievers. lt iS still meaty intellectual adventure, but all the technical language has been translated t0 people-speak within its human-sized 160 pages. lt addresses questions such as: When you want a bit more power in your game, should you go tO a heavier racquet or a lighter one? ・ What are the advantages of a racquetthat has a bigger head? ・ What effect does string tension have on your game, and hOW does it affect power and control? ・ What is the difference between gut strings and synthetic strings? ・ What is the importance Of string thickness? What is a 、 、 fast ” court and what is a "slow" court? ・ Should you adjust your equipmentto match the court speed? ・ When buying a racquet, what features should you look for? ・ If you want to put more spin on the ball, what should you do? ln my many years of playing tennis and studying tennis, I have heard a 10t 0f anecdotal answers tO these questions. ThiS bOOk gives you the answers that sci- ence and technology provide. HOWARD B RODY Physics Department University Of pennsylvania

Technical Tennis


Preface effect if they did. Understanding why a ball bounces as it does on a topspin, backspin, or sidespin shot enables you t0 ready yourself, get ⅲ position, and anticipate your return Of the shOt. lt eliminates the frustration Of being caught flat-footed and clueless time after time. lt enables you tO make intelligent cor- rections in your game. But most of all, knowing what actually happens during the hit, flight, and bounce of the ball and why れ happens is just plain fun. To be able to explain hOW and why the court, racquet, and air affect the speed, spin, and direction Of the ball—the very essence Of tennis—and thus why strokes, tactics, and strategy have evolved as they have, is a rush matched only by being able to actually do these things. Knowledge and performance combine to provide a much deeper and enjoyable tennis experience, if not a 1 れ ore successful one as well. For readers WhO are interested in the technical and scientific aspects Of tennis or are Just plain curious or are looking for an extra understanding that 、 vill give strokes and shots meaning, this b00k has been written especially for you. lt contains the results Of many years Of investigation and many experiments designed tO extract the secrets Of hOW and why tennis balls, racquets, and strings manage t0 behave the way they d0. We still don't know everything there is tO know ・ about the subject, but we know a lOt more than we used tO know.. For example, we know very little about players' perceptions 0f equip- ment properties and why they are SO Often quite different from actual measure- ments Of those properties. Likewise, we don't know why one player has a favorite string or racquet and another will think that particular strlng or rac- quet is the worst he or she has ever played with. N0t knowing all the answers makes the search an adventure, finding them out is exhilarating, and applying them raises the level of the game. Many people have contributed t0 this b00k in many ways. Ⅵ で thank all 0f them profusely, especially Howard Brody, Ron K0hn, Paul Metzler, Greg Raven, Kristine Thom, Ron Waite, Nancy Crowley, and our wives Voula and Susan.

Technical Tennis


Chapter One Go 脩 swing TenniS SWing Wrist cocked at 90 at 5 ね 代 of swing ↑ CIub pulls wrist around in line with forearm Wrist cocked at 90 。 Figure ー 」 3 The ロ 「 m slows down as the club 師 racquet speeds up. That way, energy is transferred 〇 m the ロ 「 m tO the club 0 「 racquet. A tennis serve is like an upside-down go / 「 swing. Each acts as 0 double pendulum. The wristis locked at the start Ofthe swing ⅲ 0 「 de 「 tO accelerate the club 0 「 the racquet, but the wrist should be relaxed just before impact. BALANCE POINT AND PICKUPWEIGHT At one extreme, the balance point Of a racquet is something that many players either haven't heard about or regard as a useless technical detail. At the Other extreme are professional players whO can be very fussy about the location Of their balance point. The balance point has a strong effect on hOW the racquet feels when you hold it ⅲ your hand, and it has an indirect effect on the way the racquet feels when you swing it. That's why professional players are so fussy.. They bring ontO the court five or six identical racquets, each with the same weight and with exactly the same balance point. If one Of the racquets has a different balance point, the player will notice it immediately. The balance point can be located simply by balancing a racquet across the width of the racquet using the edge 0f a ruler, or a long rod or tube. The bal- 36

Technical Tennis


TechnicaI Tennis Racquets, Strings, Balls Courts, Spin, and Bounce Rod ( 「 055 ( 「 0M0 記 Lindsey Racquet Tech Publishing Vista, Ca 鼾 0 「 nia , USA

Human Resources Kit FOR DUMMIES 3RD EDITION


Chapter 15 : Win-Win: Adding VaIue through Career Development Low-cost employee recognition perks 259 NOt every employee 「 ecognition award has tO be pricey. Here a 「 e several budget-conscious alte 「 natives: / Time 0 幵 0 「 extra vacation days / Dinner at a localrestaurant ( 0 「 a "lunch on me" coupon) / A designated employee-of-the-month park- ing spot / Tickets tO the movies 0 「 a sporting 0 「 cul- tural event / A bouquet Of flowers / A department picnic tO celeb 「 ate the achievement / GO げ 0 「 tennis lessons ( 0 「 instruction in the sport 0 「 pastime Ofthe employee's choice) / A box of fine chocolates / A book bythe staff member's ねV0 「 ite author An additionalnote: lfyou d0 hand out employee 「 ecognition awa 「 ds,they may be subject tO taxation by thelnternaIRevenue Service. Seek 厄 g advice ifyou need help dete 「 mining which awards are taxable. Some employe 「 s tack on a little extra tO Offset an employee's tax liability. ス イ i な at ル れ 4 イ CO icat ル れ Even an established recognition program doesn't run itself. You need a capa- ble administrator. Ⅱ you're handling your company's HR function, that point person may well be you. If not, it's helpfulto have one person charged with the administrative and technical duties Of running the program. That makes overall administration and troubleshooting that much easier. One Of the key components Of sound program administration is communication. Don't let yours exist in a vacuum. Even the most appealing employee recogni- tion program will prove ineffective if employees don't know that it's available. Make sure that your staff members ow which programs are in place and what the criteria are for WhO receives awards. Many firms use company intranets for such news. The initiative will be more successfulif it has support from all levels Of management ー and employees are made aware Of this. Senior manage- ment buy-in and jOint ownership ensures that the effort doesn't sit solely ー and potentially languish ー on one person's ()r department's) shoulders. ″ 4 市 out 4 : The i 可 胆 砿 ツ AIthough recognition can be handled in a personal one-on-one setting, it's Often more effective tO make the event public ー in a variety Of ways. That can help maintain enthusiasm and high levels 0f participation.

Technical Tennis


Chapter One F ↑ Pickupweight = 700 gm F 2 = 900 gm Racquet at rest Weight = 300 gm Figure 1.15 ln 0 「 de 「 t0 h01d ロ 300-gram racquetin 0 ho 「 レ 〇 n / position, you need to push up with 四 u 「 first finger (FI) and down 砒 the butt end ( F2 ). The total upward 厄 て e is 3 〇 〇 grams, but the racquet Ⅳ Ⅲ "feel" heavier than 3 〇 0 grams because the forces FI and F2 are each ロ lotlarger ロ n 3 〇 0 grams. That's because the torque due to FI ( / 〇 〇 0 gm x / 〇 cm distance 0 butt end) has to balance the torque due to the racquet weight ( 3 〇 〇 gm x 34 cm distance を om balance point tO butt end) tO stop the racquet 「 Otat ⅲ g. vince yourself of this, hold your racquet horizontal and put a weight (your car keys, for example) first on the handle and then atthe tip of the racquet. SWINGWEIGHT Swingweight is another one 0f those technical details that a player usually doesn't worry about unless he or She iS serious about tennis. professionals should definitely worry about it because their livelihoods depend on having exactly the right equipment. Even though two nominally identical racquets might have exactly the same weight and exactly the same balance point, they will feel differentto swing if each has a different swingweight. BaIance point and swingweight each depend on how the weight is distributed through the racquet and, therefore, on whether the racquet is head-light or head-heavy. Figure 1.16 details a simple example that explains the difference between weight, balance point, and swingweight. Consider a rod that is the same length as a racquet (say 700 (m) and that weighs 280 grams. The balance point will be ⅲ the middle of the rod, 350 mm from each end, if the rod has its weight uniformly distributed along its length. lt will feel the same to swing regardless of which end you hold. Now suppose we add 20 grams so the rod weighs 300 grams. Being heavier, the rod will feel heavier to hold. We can add the extra 20 grams anywhere we like, and it will still weigh 300 grams. However, the balance point and swingweight each depends ⅲ different ways on where we putthe extra 20 grams, and this will affect the way it feels to swing the rod. Consider four cases: 38

Working Effectively with Legacy Code


Working Effectively with Legacy C0de Michael C. Feathers PRENTICE HALL PTR Prentice Hall Professional Technical Reference Upper Saddle River, NJ 07458 www.phptr.com

Human Resources Kit FOR DUMMIES 3RD EDITION


346 Human Resources Kit FO 「 Dummies, 3 「 d Edition Customer Ca Ⅱ you have trouble with the CD, please call Wiley Product Technical Support at 800-762-2974. Outside the United States, call 317-572-3994. You also can contact Wiley Product TechnicaI Support at http : / / support . wi ley. co 皿 John WiIey & Sons, lnc. , will provide technical support only for installation and other general quality-controlitems. For technical support on the applica- tions themselves, consult the program's vendor or author. TO place additional orders or tO request information about Other Wiley products, please call 877-762-2974.

Software security. building security in


44 C わ 4 2 A R な た Ma 〃 ag ビ 川 厩 孖 4 川 e 曜 0 黻 Business risk identification helps tO define and steer use Of particular technical methods for extracting, measurmg, and mitigating software risk glven var1011S software artifacts. identification Of business riSkS a necessary foundation that allows software risk (especially impact) t0 be quantified and described in business terms. ThiS makes impact statements tangible and spurs actl()n on risk mitigation. The key to making risk management work for any business lies in tying technical risks tO the business context in a meaningful way. The ability tO thoroughly identify and understand risks is thus essential. Uncovering and recognizing technical risks is a high-expertise undertaking that usually reqtllres years Of expenence. But their Of the technical risks are Often not actionable. central to this stage of the RMF is the ability t0 discover and describe technical risks and map them (through business risks) t0 business goals. A technical risk is a situation that runs counter tO the planned design or imple- mentatlon Of the system under consideration. For example, a technical risk may tO the system behaving ln an unexpected way' violating its own design strictures, or failing t0 perform as required. If the builders d0 not make proper use 0f touchpoints, these kinds 0f risks may slip bY unnoticed. Technical risks can also be related to the process of building software. The process an organization f0110 、 may Offer t00 many opportunities for mlS- takes in design or implementation. Technical risks involve impacts such as unexpected system crashes, avoidance Of controls (audit or otherwise)' unauthorized data modification or disclosure, and needless rework Of arti- facts during development. Technical risk identification is supported by the software security touch- points described throughout this b00k. stage 3 : Synthesize and Rank the Risks Large numbers 0f risks will be apparent in almost any given system. ldenti- fying these risks is important, but it is the prioritization Of them that leads directly tO creation Of value. Through the activities Of synthesizing and pri- oritizing risks, the critical 。 。 / hO cares ' question can (and must) be answered. synthesis and prioritization should be driven tO answer questions such as: "What shall we dO first given the current risk situation?" and "\Vhat is the best allocatlon Of resources, especially in terms Of risk mitiga- tlon activities ' clearly, the prioritlzatlon process must take int() account which business goals are the most lmportant tO the organization' which goals are immediately threatened, and how likely technical risks are t0

Technical Tennis


Chapter Three Ba 騰 and Bounce 旧 the blink of an eye 0 bouncing ball slows, changes its spin, slides across and bites intO the court and st 「 ings, squashes and stretches, and rebounds. The very nature Of the game depends on this 5-millisecond sequence Of events. BALL BASICS BALL HISTORY TenniS balls were used many centuries ago in France When they were made from leather and filled with wool or cloth. HoIIow rubber tennis balls were used for the first Wimbledon Championships ⅲ 1872 , but by 1875 they were covered ⅲ white c10 市 stitched 0m0 the ball because of their better playing characteristics. Almost nothing has changed since then, apart frOI れ the compo- sition of the rubber and the cloth. If you remove the cloth from a modern ten- nis ball, you will have almost exactly the same 40-gram, 51-mm diameter rub- ber ball that was used for the 1872 Championships. ln some respects the old rubber ball is easier to play with because it feels a 10t lighter, butthe bounce and flight through the air are a bit erratic. A 40-gram ball is not a whole 10t lighter than a 57-gram ball, but ⅱ feels a whole lotlighter because a rubber ball without its clOth cover is much SOfter. The force on the strings, transmitted through the racquet tO the arm, is therefore a 10 [ smaller. RULES ABOUT BALLS There are more rules in the game of tennis about tennis balls than there are about tennis racquets, strings, or courts. You can play with a five-pound brass racquet strung with fencing wire on an uphill cow paddock according to the 87