SA 60s Science

Forest Canopy Color Reveals CO2 Uptake

Trees take carbon dioxide, or CO2, from the atmosphere and convert it into biomass. By sopping up CO2 they help to stabilize the climate. But at the same time, they’re also affected by climate, for example, budding earlier in the season as global temperatures rise.
To understand how all this balances out, ecologists monitor how forests take up CO2. It’s a costly business that involves using a network of 500 instrument towers worldwide. So researchers got to wondering whether there might be an easier way to keep an eye on photosynthesis. And they found that digital cameras do the trick.
Analyzing two years’ worth of snaps taken every half hour in a forest in southern England, the researchers discovered that a tree’s leafy colors provide a good proxy for its photosynthetic productivity. So next time you go for a walk in the woods, take only photos. And leave only data points.

Humidity Levels Explain U.S. Flu Winter Peak 

Cases of the flu peak in winter in the U.S. But why? A new study suggests it’s not the heat, but the humidity. Or lack thereof. Because in temperate regions, the influenza virus fares best when the weather is dry. That’s according to work published in the journal PLoS One. [Wan Yang, Subbiah Elankumaran and Linsey C. Marr, Relationship between Humidity and Influenza A Viability in Droplets and Implications for Influenza’s Seasonality]
Scientists have long debated why flu erupts when the days grow chilly. Is it that we spend more time cooped up together indoors? Or is there something about the virus that likes it cold and dry? To find out, researchers suspended influenza virus in a solution that mimics human mucus. They incubated this infectious soup at different humidities and measured viral survival.
And they found that at low humidity, the fake mucus dries up and the virus does just fine. But when the humidity tops 50%, the droplets only partially evaporate, leaving behind a solution that’s too salty for the virus to thrive.
Interestingly, the virus does well again when the humidity reaches 100 percent, evaporation stops and the salinity of the mucus bath is juuust right. That could explain why the flu prefers to hit the tropics in rainy season. And why you should always keep your nose clean, but moist.

計算acos的簡單範例，先用以下公式求出cos值，再利用acos得到角度

/* acos example */
#include <stdio.h>
#include <math.h>

#define PI 3.14159265

int main ()
{
  double param, result;
  param = 0.5;
  result = acos (param) * 180.0 / PI;
  printf ("The arc cosine of %lf is %lf degrees.\n", param, result );
  return 0;
}

參考

• cplusplus.com
• Dihedraal angle

這個禮拜最令我傷神的，不過幸好很久以前有想過一次，所以要回復記憶比較沒有那麼困難。首先我先把C++版本的linked list刻出來，當然骨幹是參考別人的，然後自己有改了些東西，沒花多久時間很快就用出來了。

以下是標頭檔：

class CKLinkList{
    private:
        struct node {
            int x;
            int y;
            int z;
            node *link;
        } *p;

        int count_i;

    public:
        CKLinkList();
        void append(int);
        void insert_after(int,int);
        void insert_first(int);

        void display(void);
        void display_line(void);
        int length(void);
        void del(int);
        ~CKLinkList();
};

接下來是實作

#include <iostream>
#include "linklist.h"

using namespace std;

CKLinkList::CKLinkList(){
    p = NULL;
    count_i = 0;
};

int CKLinkList::length(){
    return count_i;
};

void CKLinkList::del(int num){
    node *q, *r;
    q = p;

    // No node
    if (p == NULL) return;

    // Delete the first node
    if (q->x == num){
        p = q->link;
        delete q;
        count_i--;
        return;
    }

    // Delete the remainder
    r = q;
    while( q != NULL){
        if (q->x == num){
            r->link = q->link;
            delete q;
            count_i--;
            return;
        }

        r = q;
        q = q->link;
    }
};

void CKLinkList::insert_first(int num){

    node *q, *t;
    q = p;

    t = new node;
    t->x = num;
    t->y = num*2;
    t->z = num*3;

    t->link = q;
    p = t;
    count_i++;
};

void CKLinkList::insert_after(int start_val,int num){
    node *q, *t;

    if (start_val != 0){
        q = p;
        while(q->link != NULL){
            if (q->x == start_val){

                t = new node;
                t->x = num;
                t->y = num*2;
                t->z = num*3;
                t->link = q->link;
                q->link = t;

                count_i++;
                return;
            }

            q = q->link;
        }
    }
};

void CKLinkList::append(int num){
    node *q, *t;

    if (p == NULL){
        p = new node;
        p->x = num;
        p->y = num*2;
        p->z = num*3;
        p->link = NULL;
    } else {
        q = p;
        while(q->link != NULL){
            q = q->link;
        }

        t = new node;
        t->x = num;
        t->y = num*2;
        t->z = num*3;
        t->link = NULL;
        q->link = t;
    }

    count_i++;
};

void CKLinkList::display_line(void){
    node *q;

    for(q = p; q != NULL; q = q->link){
        cout << " <- " << q->x;
    }

    cout << endl;
};

void CKLinkList::display(void){
    node *q;

    for(q = p; q != NULL; q = q->link){
        cout << "This is : " << q->x << ", " << q->y << ", " << q->z << endl;
    }
};

CKLinkList::~CKLinkList(){
    node *q;
    if (p == NULL) return;

    while (p != NULL){
        q = p->link;
        delete p;
        p = q;
    }
};

接下來我看到了一個使用C++ template去實作的版本，應該說是某個老師的教學課程(參考第10,11,12章)，我就順便把她的課程講義看過一遍，然後把他的版本做出來。第一次使用C++的template，雖然滿麻煩的，但是真的是很強大，看來以後搞不好我的每個程式都要用template去做出來。以下是template的版本：

#include <iostream>
using namespace std;

template <class T>
class ChainNode {
    private:

    public:
        T data;
        ChainNode<T> *link;

        ChainNode(void){};
        ChainNode(const T& data){ this->data = data; };
        ChainNode(const T& data, ChainNode<T> *link){
            this->data = data;
            this->link = link;
        };
};

template <class T>
class Chain {
    private:
        ChainNode<T> *first;
        int count;

    public:
        Chain(void){ first = NULL; count = 0; };
        bool isEmpty() const {return first == NULL;}
        int IndexOf(const T&) const;
        int size(void){return count;}
        void Delete(int);
        void Insert(int,const T&);
        void Display(void);
        ~Chain();
};

// Destruction
template <class T>
Chain<T>::~Chain() {

    while (first != NULL){
        ChainNode<T> *next = first->link;
        delete first;
        first = next;
    }
};

template <class T>
int Chain<T>::IndexOf(const T& theElement) const{

    ChainNode<T> *currentNode = first;
    int index = 0;
    while(currentNode != NULL && currentNode->data != theElement){
        currentNode = currentNode->link;
        index++;
    }

    if (currentNode == NULL)
        return -1;
    else
        return index;
};

template <class T>
void Chain<T>::Delete(int theIndex){
    if (first == NULL) throw "Can not delete empty chain";

    ChainNode<T> *deleteNode;
    if (theIndex == 0){
        deleteNode = first;
        first = first->link;
        delete deleteNode;
        count--;

    } else {
        ChainNode<T> *p = first;
        for(int i =0; i< theIndex-1; i++){
            if (p == NULL) throw "Element not exist";
            p = p->link;
        }

        deleteNode = p->link;
        p->link = p->link->link;
        delete deleteNode;
        count--;
    }
}

template <class T>
void Chain<T>::Insert(int theIndex, const T& theElement){
    if (theIndex < 0) throw "Bad";

    if (theIndex == 0){
        first = new ChainNode<T>(theElement,first);
        count++;
    } else {
        ChainNode<T> *p = first;
        for(int i = 0; i < theIndex-1; i++){
            if (p == NULL) throw "Not Exist";
            p = p->link;
        }
        
        p->link = new ChainNode<T>(theElement, p->link);
        count++;
    }
};

template <class T>
void Chain<T>::Display(void){

    ChainNode<T> *p = first;

    while(p != NULL){
        cout << " <- " << p->data;
        p = p->link;
    }
    cout << endl;
};

int main() {
    cout << "This is LinkList .." << endl;

    Chain<int> *list = new Chain<int>;
    cout << "Size: " << list->size() << endl;

    list->Insert(0,1);
    list->Display();
    list->Insert(0,2);
    list->Display();
    list->Insert(1,3);
    list->Display();
    list->Insert(1,4);
    list->Display();
    list->Insert(0,5);
    list->Display();
    list->Delete(2);
    list->Display();

    cout << "Size: " << list->size() << endl;
}

繼續努力加油吧，這星期把linked list搞完之後還有很多要充實的，以上的source code都公布在github上看(其實blog根本不適合看這麼多程式碼是吧XD)。

剛剛喵了一下我的跑步計畫，Tempo Run的配速看了之後覺得還有些不輕鬆。約8KM的距離速度在pace 5左右。根據最近這兩個禮拜在操場跑下來的結果，似乎400m@120s需要熱個將近10圈之後才有可能，所以我看短時間還是先把目標速訂在130s然後再慢慢加到120s。

從網路上轉貼來的sublime2快捷鍵，我想我應該滿需要的